Hi,

As the subject reads, use the more predictable %F, aka %Y-%m-%d, instead
of %G-%m-%d. The latter follows the definition of ISO-8601 week-based
year, which is weird. Citing what POSIX [0] says about it:

> %g, %G, and %V give values according to the ISO 8601:2000 standard
> week-based year. In this system, weeks begin on a Monday and week 1 of
> the year is the week that includes January 4th, which is also the week
> that includes the first Thursday of the year, and is also the first
> week that contains at least four days in the year. If the first Monday
> of January is the 2nd, 3rd, or 4th, the preceding days are part of the
> last week of the preceding year; thus, for Saturday 2nd January 1999,
> %G is replaced by 1998 and %V is replaced by 53. If December 29th,
> 30th, or 31st is a Monday, it and any following days are part of week
> 1 of the following year. Thus, for Tuesday 30th December 1997, %G is
> replaced by 1998 and %V is replaced by 01.

In particular, 2024 is one of such years with weird behaviour:

	$ date -jf %Y-%m-%d +"%F %G-%m-%d" 2024-12-30
	2024-12-30 2025-12-30

The changes were performed mechanically with

	sed -i 's/%G-%m-%d/%F/g' $(grep -Flr %G-%m-%d)

All the uses of %G-%m-%d come from either date(1) or strftime(3). No
other %G is left around the repo. Given that %F is shorter, I unfolded
a couple of lines. make regress is happy.

	Lucas

[0]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/strftime.html


-----------------------------------------------
commit dac05127ab3a70fb5cc6a76467ff101fe583b0ee (strftime-G)
from: Lucas Gabriel Vuotto <lucas@lgv5.net>
date: Tue Apr 23 18:27:34 2024 UTC
 
 Replace date, strftime %G-%m-%d with %F
 
 The %G specifier is the ISO-8601 week-based year, which differs from the
 calendar year under certain circumstances. Replace it with %Y to follow
 the calendar year. Given that %F is %Y-%m-%d, use %F instead.
 
diff b93f334d743a91156b4558df907bd59a0c85cf69 dac05127ab3a70fb5cc6a76467ff101fe583b0ee
commit - b93f334d743a91156b4558df907bd59a0c85cf69
commit + dac05127ab3a70fb5cc6a76467ff101fe583b0ee
blob - 38191d6109e5f5caf08654969f4f3af3d9fb2c70
blob + 8371183b94f386e42d65020ff1fed931a40906e3
--- cvg/cvg.c
+++ cvg/cvg.c
@@ -3552,7 +3552,7 @@ print_commit_oneline(struct got_commit_object *commit,
 		err = got_error_from_errno("gmtime_r");
 		goto done;
 	}
-	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d ", &tm) == 0) {
+	if (strftime(datebuf, sizeof(datebuf), "%F ", &tm) == 0) {
 		err = got_error(GOT_ERR_NO_SPACE);
 		goto done;
 	}
@@ -4989,8 +4989,7 @@ blame_cb(void *arg, int nlines, int lineno,
 	committer_time = got_object_commit_get_committer_time(commit);
 	if (gmtime_r(&committer_time, &tm) == NULL)
 		return got_error_from_errno("gmtime_r");
-	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%G-%m-%d",
-	    &tm) == 0) {
+	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%F", &tm) == 0) {
 		err = got_error(GOT_ERR_NO_SPACE);
 		goto done;
 	}
blob - b55e991971271638732739463b3a95ee39f126af
blob + 9b22bd01524107cae5a5dc3a2b85913cadb5bd7b
--- got/got.c
+++ got/got.c
@@ -4252,7 +4252,7 @@ print_commit_oneline(struct got_commit_object *commit,
 		err = got_error_from_errno("gmtime_r");
 		goto done;
 	}
-	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d ", &tm) == 0) {
+	if (strftime(datebuf, sizeof(datebuf), "%F ", &tm) == 0) {
 		err = got_error(GOT_ERR_NO_SPACE);
 		goto done;
 	}
@@ -5728,8 +5728,7 @@ blame_cb(void *arg, int nlines, int lineno,
 	committer_time = got_object_commit_get_committer_time(commit);
 	if (gmtime_r(&committer_time, &tm) == NULL)
 		return got_error_from_errno("gmtime_r");
-	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%G-%m-%d",
-	    &tm) == 0) {
+	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%F", &tm) == 0) {
 		err = got_error(GOT_ERR_NO_SPACE);
 		goto done;
 	}
@@ -10968,7 +10967,7 @@ get_commit_brief_str(char **brief_str, struct got_comm
 	committer_time = got_object_commit_get_committer_time(commit);
 	if (gmtime_r(&committer_time, &tm) == NULL)
 		return got_error_from_errno("gmtime_r");
-	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d", &tm) == 0)
+	if (strftime(datebuf, sizeof(datebuf), "%F", &tm) == 0)
 		return got_error(GOT_ERR_NO_SPACE);
 
 	author0 = strdup(got_object_commit_get_author(commit));
blob - 16f1d741593d53dc9c972d53a4536edabae0301a
blob + 931efceb0756948a547a10f4e697267b1e11010c
--- gotd/libexec/got-notify-email/got-notify-email.c
+++ gotd/libexec/got-notify-email/got-notify-email.c
@@ -243,7 +243,7 @@ print_date(int s, char *date, int shortfmt)
 		return got_poll_write_full(s, " UTC\n", 5);
 	}
 
-	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d ", &tm) == 0)
+	if (strftime(datebuf, sizeof(datebuf), "%F ", &tm) == 0)
 		return got_error_set_errno(EINVAL, "invalid timestamp");
 	return got_poll_write_full(s, datebuf, strlen(datebuf));
 }
blob - bd3939fbbae66ba3fc54ef4ac319959561b56a2c
blob + 5bcdf61f67c447df889e0dce4ed81ce7e39d19e0
--- gotwebd/got_operations.c
+++ gotwebd/got_operations.c
@@ -944,8 +944,7 @@ got_gotweb_blame_cb(void *arg, int nlines, int lineno,
 	committer_time = got_object_commit_get_committer_time(commit);
 	if (gmtime_r(&committer_time, &tm) == NULL)
 		return got_error_from_errno("gmtime_r");
-	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%G-%m-%d",
-	    &tm) == 0) {
+	if (strftime(bline->datebuf, sizeof(bline->datebuf), "%F", &tm) == 0) {
 		err = got_error(GOT_ERR_NO_SPACE);
 		goto done;
 	}
blob - 4281311847e1767c625823074c5208dc9f177123
blob + d60fc3d989f80b6803c66daddd2280f9ac6bee96
--- regress/cmdline/blame.sh
+++ regress/cmdline/blame.sh
@@ -65,7 +65,7 @@ test_blame_basic() {
 	local short_commit2=`trim_obj_id 32 $commit2`
 	local short_commit3=`trim_obj_id 32 $commit3`
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit1 $d $GOT_AUTHOR_8 1" > $testroot/stdout.expected
 	echo "2) $short_commit2 $d $GOT_AUTHOR_8 2" >> $testroot/stdout.expected
 	echo "3) $short_commit3 $d $GOT_AUTHOR_8 3" >> $testroot/stdout.expected
@@ -113,7 +113,7 @@ test_blame_tag() {
 	local short_commit1=`trim_obj_id 32 $commit1`
 	local short_commit2=`trim_obj_id 32 $commit2`
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit1 $d $GOT_AUTHOR_8 1" > $testroot/stdout.expected
 	echo "2) $short_commit2 $d $GOT_AUTHOR_8 2" >> $testroot/stdout.expected
 
@@ -149,7 +149,7 @@ test_blame_file_single_line() {
 
 	local short_commit1=`trim_obj_id 32 $commit1`
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit1 $d $GOT_AUTHOR_8 1" > $testroot/stdout.expected
 
 	cmp -s $testroot/stdout.expected $testroot/stdout
@@ -184,7 +184,7 @@ test_blame_file_single_line_no_newline() {
 
 	local short_commit1=`trim_obj_id 32 $commit1`
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit1 $d $GOT_AUTHOR_8 1" > $testroot/stdout.expected
 
 	cmp -s $testroot/stdout.expected $testroot/stdout
@@ -213,7 +213,7 @@ test_blame_all_lines_replaced() {
 
 	(cd $testroot/wt && got blame alpha > $testroot/stdout)
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit1 $d $GOT_AUTHOR_8 1" > $testroot/stdout.expected
 	echo "2) $short_commit1 $d $GOT_AUTHOR_8 2" >> $testroot/stdout.expected
 	echo "3) $short_commit1 $d $GOT_AUTHOR_8 3" >> $testroot/stdout.expected
@@ -268,7 +268,7 @@ test_blame_lines_shifted_up() {
 
 	(cd $testroot/wt && got blame alpha > $testroot/stdout)
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit1 $d $GOT_AUTHOR_8 1" > $testroot/stdout.expected
 	echo "2) $short_commit1 $d $GOT_AUTHOR_8 2" >> $testroot/stdout.expected
 	echo "3) $short_commit3 $d $GOT_AUTHOR_8 foo" >> $testroot/stdout.expected
@@ -327,7 +327,7 @@ test_blame_lines_shifted_down() {
 
 	(cd $testroot/wt && got blame alpha > $testroot/stdout)
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "01) $short_commit1 $d $GOT_AUTHOR_8 1" \
 		> $testroot/stdout.expected
 	echo "02) $short_commit1 $d $GOT_AUTHOR_8 2" \
@@ -400,7 +400,7 @@ EOF
 	local commit1=`git_show_head $testroot/repo`
 	local short_commit1=`trim_obj_id 32 $commit1`
 	local author_time1=`git_show_author_time $testroot/repo`
-	local d1=`date -u -r $author_time1 +"%G-%m-%d"`
+	local d1=`date -u -r $author_time1 +"%F"`
 
 	cat > $testroot/wt/alpha <<EOF
 SUBDIRS = ext modules codedocs docs
@@ -427,7 +427,7 @@ EOF
 	local commit2=`git_show_head $testroot/repo`
 	local short_commit2=`trim_obj_id 32 $commit2`
 	local author_time2=`git_show_author_time $testroot/repo`
-	local d2=`date -u -r $author_time2 +"%G-%m-%d"`
+	local d2=`date -u -r $author_time2 +"%F"`
 
 	cat > $testroot/wt/alpha <<EOF
 SUBDIRS = ext modules pdns codedocs docs
@@ -451,7 +451,7 @@ EOF
 	local commit3=`git_show_head $testroot/repo`
 	local short_commit3=`trim_obj_id 32 $commit3`
 	local author_time3=`git_show_author_time $testroot/repo`
-	local d3=`date -u -r $author_time3 +"%G-%m-%d"`
+	local d3=`date -u -r $author_time3 +"%F"`
 
 	cat > $testroot/wt/alpha <<EOF
 SUBDIRS = ext modules pdns codedocs docs
@@ -475,7 +475,7 @@ EOF
 	local commit4=`git_show_head $testroot/repo`
 	local short_commit4=`trim_obj_id 32 $commit4`
 	local author_time4=`git_show_author_time $testroot/repo`
-	local d4=`date -u -r $author_time4 +"%G-%m-%d"`
+	local d4=`date -u -r $author_time4 +"%F"`
 
 	(cd $testroot/wt && got blame alpha > $testroot/stdout)
 
@@ -724,7 +724,7 @@ test_blame_added_on_branch() {
 	local short_commit2=`trim_obj_id 32 $commit2`
 	local short_commit3=`trim_obj_id 32 $commit3`
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit1 $d $GOT_AUTHOR_8 1" > $testroot/stdout.expected
 	echo "2) $short_commit2 $d $GOT_AUTHOR_8 2" >> $testroot/stdout.expected
 	echo "3) $short_commit3 $d $GOT_AUTHOR_8 3" >> $testroot/stdout.expected
@@ -795,7 +795,7 @@ test_blame_symlink() {
 		return 1
 	fi
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit0 $d $GOT_AUTHOR_8 alpha" \
 		> $testroot/stdout.expected
 
@@ -816,7 +816,7 @@ test_blame_symlink() {
 		return 1
 	fi
 
-	d=`date -u -r $author_time +"%G-%m-%d"`
+	d=`date -u -r $author_time +"%F"`
 	echo "1) $short_commit0 $d $GOT_AUTHOR_8 beta" \
 		> $testroot/stdout.expected
 
@@ -966,10 +966,10 @@ EOF
 
 	(cd $testroot/wt && got blame alpha > $testroot/stdout)
 
-	d1=`date -u -r $author_time1 +"%G-%m-%d"`
-	d2=`date -u -r $author_time2 +"%G-%m-%d"`
-	d4=`date -u -r $author_time4 +"%G-%m-%d"`
-	d5=`date -u -r $author_time5 +"%G-%m-%d"`
+	d1=`date -u -r $author_time1 +"%F"`
+	d2=`date -u -r $author_time2 +"%F"`
+	d4=`date -u -r $author_time4 +"%F"`
+	d5=`date -u -r $author_time5 +"%F"`
 	echo "1) $short_commit5 $d5 $GOT_AUTHOR_8 X" > $testroot/stdout.expected
 	echo "2) $short_commit1 $d1 $GOT_AUTHOR_8 A" >> $testroot/stdout.expected
 	echo "3) $short_commit1 $d1 $GOT_AUTHOR_8 B" >> $testroot/stdout.expected
@@ -1042,7 +1042,7 @@ test_blame_commit_keywords() {
 	done
 
 	local author_time=$(git_show_author_time "$repo")
-	local d=$(date -u -r $author_time +"%G-%m-%d")
+	local d=$(date -u -r $author_time +"%F")
 
 	got blame -r "$repo" -c:head:-8 alpha > "$testroot/stdout"
 	echo "1) $(pop_idx 1 $@) $d $GOT_AUTHOR_8 alpha" > \
blob - 13dd31e4feec963e558e3e0eebbcfac22c15c741
blob + b0adfd36a468c7760119682e77e3c30152401592
--- regress/cmdline/histedit.sh
+++ regress/cmdline/histedit.sh
@@ -156,10 +156,10 @@ test_histedit_no_op() {
 
 	# We should have a backup of old commits
 	(cd $testroot/repo && got histedit -l > $testroot/stdout)
-	d_orig1=`date -u -r $old_author_time1 +"%G-%m-%d"`
+	d_orig1=`date -u -r $old_author_time1 +"%F"`
 	d_orig2=`date -u -r $old_author_time2 +"%a %b %e %X %Y UTC"`
-	d_new2=`date -u -r $new_author_time2 +"%G-%m-%d"`
-	d_orig=`date -u -r $orig_author_time +"%G-%m-%d"`
+	d_new2=`date -u -r $new_author_time2 +"%F"`
+	d_orig=`date -u -r $orig_author_time +"%F"`
 	cat > $testroot/stdout.expected <<EOF
 -----------------------------------------------
 commit $old_commit2 (formerly master)
blob - c3e22d2178b4eebd38723079274f19c9e8b9d2d5
blob + 2f9468695f6cf968b15297cfe13f3ecee0544e73
--- regress/cmdline/log.sh
+++ regress/cmdline/log.sh
@@ -319,9 +319,9 @@ no" > /dev/null)
 	local commit_id2=`git_show_head $testroot/repo`
 	local author_time2=`git_show_author_time $testroot/repo`
 
-	d=`date -u -r $author_time1 +"%G-%m-%d"`
+	d=`date -u -r $author_time1 +"%F"`
 	printf "$d %-7s test oneline\n" master > $testroot/stdout.expected
-	d=`date -u -r $author_time2 +"%G-%m-%d"`
+	d=`date -u -r $author_time2 +"%F"`
 	printf "$d %.7s test oneline\n" $commit_id1 >> $testroot/stdout.expected
 
 	(cd $testroot/repo && got log -s | head -n 2 > $testroot/stdout)
@@ -963,7 +963,7 @@ EOF
 test_log_commit_keywords() {
 	local testroot=$(test_init log_commit_keywords)
 	local commit_time=`git_show_author_time $testroot/repo`
-	local d=`date -u -r $commit_time +"%G-%m-%d"`
+	local d=`date -u -r $commit_time +"%F"`
 
 	set -- "$(git_show_head $testroot/repo)"
 
@@ -1280,11 +1280,11 @@ test_log_toposort() {
 	local short_commit2=`trim_obj_id 33 $commit2`
 	local short_commit3=`trim_obj_id 33 $commit3`
 
-	d_0=`date -u -r $author_time0 +"%G-%m-%d"`
-	d_1=`date -u -r $author_time1 +"%G-%m-%d"`
-	d_2=`date -u -r $author_time2 +"%G-%m-%d"`
-	d_3=`date -u -r $author_time3 +"%G-%m-%d"`
-	d_m=`date -u -r $merge_time +"%G-%m-%d"`
+	d_0=`date -u -r $author_time0 +"%F"`
+	d_1=`date -u -r $author_time1 +"%F"`
+	d_2=`date -u -r $author_time2 +"%F"`
+	d_3=`date -u -r $author_time3 +"%F"`
+	d_m=`date -u -r $merge_time +"%F"`
 
 	got log -r $testroot/repo -s -b -t > $testroot/stdout
 	cat > $testroot/stdout.expected <<EOF
blob - ee6fefa31ac2365004dd760838761c9cba5e07a1
blob + fae088133932111b4944a156b5ea1ac14d52df37
--- regress/cmdline/rebase.sh
+++ regress/cmdline/rebase.sh
@@ -154,8 +154,8 @@ test_rebase_basic() {
 	# We should have a backup of old commits
 	(cd $testroot/repo && got rebase -l > $testroot/stdout)
 	d_orig2=`date -u -r $orig_author_time2 +"%a %b %e %X %Y UTC"`
-	d_new2=`date -u -r $new_author_time2 +"%G-%m-%d"`
-	d_0=`date -u -r $commit0_author_time +"%G-%m-%d"`
+	d_new2=`date -u -r $new_author_time2 +"%F"`
+	d_0=`date -u -r $commit0_author_time +"%F"`
 	cat > $testroot/stdout.expected <<EOF
 -----------------------------------------------
 commit $orig_commit2 (formerly newbranch)
blob - 807c18616e33a8a87ad3db0a355f974f13c8622d
blob + f95b00932a0932131a46023cbdd33283f82a5563
--- regress/gotd/email_notification.sh
+++ regress/gotd/email_notification.sh
@@ -202,7 +202,7 @@ test_many_commits_summarized() {
 		local commit_id=`git_show_head $testroot/repo-clone`
 		local short_commit_id=`trim_obj_id 33 $commit_id`
 		local author_time=`git_show_author_time $testroot/repo-clone`
-		d=`date -u -r $author_time +"%G-%m-%d"`
+		d=`date -u -r $author_time +"%F"`
 		set -- "$@" "$short_commit_id $d"
 	done
 
blob - 9f57e1d06d86371e2c8f959955561a8b2d951823
blob + 2a1df1daa4d10bc1df74a5b3e633844cb71a60eb
--- regress/tog/blame.sh
+++ regress/tog/blame.sh
@@ -41,7 +41,7 @@ test_blame_basic()
 	(cd $testroot/wt && got commit -m "c change" > /dev/null)
 	local commit_id4=`git_show_head $testroot/repo`
 	local author_time=`git_show_author_time $testroot/repo`
-	local ymd=`date -u -r $author_time +"%G-%m-%d"`
+	local ymd=`date -u -r $author_time +"%F"`
 
 	cat <<EOF >$TOG_TEST_SCRIPT
 WAIT_FOR_UI	wait for blame to finish
@@ -83,7 +83,7 @@ test_blame_commit_keywords()
 	local wt="$testroot/wt"
 	local id=$(git_show_head "$repo")
 	local author_time=$(git_show_author_time "$repo")
-	local ymd=$(date -u -r $author_time +"%G-%m-%d")
+	local ymd=$(date -u -r $author_time +"%F")
 
 	set -- "$id"
 
@@ -168,7 +168,7 @@ test_blame_commit_keywords()
 	done
 
 	author_time=$(git_show_author_time "$repo")
-	ymd=$(date -u -r $author_time +"%G-%m-%d")
+	ymd=$(date -u -r $author_time +"%F")
 
 	# :base:- keyword in work tree
 	cat <<-EOF >$testroot/view.expected
blob - bc8e1f86537b6f5d928c84cdd4144af824835317
blob + aca1f106300cbd9e2079fa5bedad94acb5af6f36
--- regress/tog/log.sh
+++ regress/tog/log.sh
@@ -23,7 +23,7 @@ test_log_hsplit_diff()
 	local head_id=`git_show_head $testroot/repo`
 	local author_time=`git_show_author_time $testroot/repo`
 	local date=`date -u -r $author_time +"%a %b %e %X %Y UTC"`
-	local ymd=`date -u -r $author_time +"%G-%m-%d"`
+	local ymd=`date -u -r $author_time +"%F"`
 
 	cat <<EOF >$TOG_TEST_SCRIPT
 KEY_ENTER	open diff view of selected commit
@@ -78,7 +78,7 @@ test_log_vsplit_diff()
 	local head_id=`git_show_head $testroot/repo`
 	local author_time=`git_show_author_time $testroot/repo`
 	local date=`date -u -r $author_time +"%a %b %e %X %Y UTC"`
-	local ymd=`date -u -r $author_time +"%G-%m-%d"`
+	local ymd=`date -u -r $author_time +"%F"`
 	local blobid_alpha=`get_blob_id $testroot/repo "" alpha`
 	local blobid_beta=`get_blob_id $testroot/repo "" beta`
 
@@ -134,7 +134,7 @@ test_log_show_author()
 	local head_id=`git_show_head $testroot/repo`
 	local author_time=`git_show_author_time $testroot/repo`
 	local date=`date -u -r $author_time +"%a %b %e %X %Y UTC"`
-	local ymd=`date -u -r $author_time +"%G-%m-%d"`
+	local ymd=`date -u -r $author_time +"%F"`
 	local head_id_len8=`trim_obj_id 32 $head_id`
 
 	echo "mod alpha" > $testroot/repo/alpha
@@ -177,7 +177,7 @@ test_log_scroll_right()
 	local head_id=`git_show_head $testroot/repo`
 	local author_time=`git_show_author_time $testroot/repo`
 	local date=`date -u -r $author_time +"%a %b %e %X %Y UTC"`
-	local ymd=`date -u -r $author_time +"%G-%m-%d"`
+	local ymd=`date -u -r $author_time +"%F"`
 	local msg="scroll this log message to the right four characters"
 	local scrolled_msg="ter] scroll this log message to the right four character"
 
@@ -217,7 +217,7 @@ test_log_hsplit_ref()
 	local head_id=`git_show_head $testroot/repo`
 	local author_time=`git_show_author_time $testroot/repo`
 	local date=`date -u -r $author_time +"%a %b %e %X %Y UTC"`
-	local ymd=`date -u -r $author_time +"%G-%m-%d"`
+	local ymd=`date -u -r $author_time +"%F"`
 
 	cat <<EOF >$TOG_TEST_SCRIPT
 R		open ref view
@@ -258,7 +258,7 @@ test_log_hsplit_tree()
 	local head_id=`git_show_head $testroot/repo`
 	local author_time=`git_show_author_time $testroot/repo`
 	local date=`date -u -r $author_time +"%a %b %e %X %Y UTC"`
-	local ymd=`date -u -r $author_time +"%G-%m-%d"`
+	local ymd=`date -u -r $author_time +"%F"`
 
 	cat <<EOF >$TOG_TEST_SCRIPT
 T		open tree view
@@ -361,7 +361,7 @@ test_log_commit_keywords()
 	local wt="$testroot/wt"
 	local id=$(git_show_head "$repo")
 	local author_time=$(git_show_author_time "$repo")
-	local ymd=$(date -u -r $author_time +"%G-%m-%d")
+	local ymd=$(date -u -r $author_time +"%F")
 
 	set -- "$id"
 
@@ -519,7 +519,7 @@ test_log_show_base_commit()
 
 	local head_id=$(git_show_head "$repo")
 	local author_time=$(git_show_author_time "$repo")
-	local ymd=$(date -u -r "$author_time" +"%G-%m-%d")
+	local ymd=$(date -u -r "$author_time" +"%F")
 
 	# check up-to-date base commit marker prefixes base commit log message
 	cat <<-EOF >$TOG_TEST_SCRIPT
@@ -638,7 +638,7 @@ test_log_limit_view()
 		return 1
 	fi
 	local author_time=$(git_show_author_time "$repo")
-	local ymd=$(date -u -r $author_time +"%G-%m-%d")
+	local ymd=$(date -u -r $author_time +"%F")
 	local id=$(git_show_head "$repo")
 
 	# check base commit marker is not drawn
@@ -698,7 +698,7 @@ test_log_search()
 	done
 
 	local author_time=$(git_show_author_time "$repo")
-	local ymd=$(date -u -r $author_time +"%G-%m-%d")
+	local ymd=$(date -u -r $author_time +"%F")
 
 	cat <<-EOF >$TOG_TEST_SCRIPT
 	/alpha commit 8
blob - 49be7dc0e431407602c4dba0ac7030028d5a567e
blob + ef69429eb4ba2e561f99ebcf790e0f123f4d05cb
--- tog/tog.c
+++ tog/tog.c
@@ -2459,7 +2459,7 @@ draw_commit(struct tog_view *view, struct commit_queue
 	committer_time = got_object_commit_get_committer_time(commit);
 	if (gmtime_r(&committer_time, &tm) == NULL)
 		return got_error_from_errno("gmtime_r");
-	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d ", &tm) == 0)
+	if (strftime(datebuf, sizeof(datebuf), "%F ", &tm) == 0)
 		return got_error(GOT_ERR_NO_SPACE);
 
 	if (avail <= date_display_cols)
@@ -8790,7 +8790,7 @@ show_ref_view(struct tog_view *view)
 			free(id);
 			if (gmtime_r(&t, &tm) == NULL)
 				return got_error_from_errno("gmtime_r");
-			if (strftime(ymd, sizeof(ymd), "%G-%m-%d  ", &tm) == 0)
+			if (strftime(ymd, sizeof(ymd), "%F  ", &tm) == 0)
 				return got_error(GOT_ERR_NO_SPACE);
 		}
 		if (got_ref_is_symbolic(re->ref)) {