From bf2e078ecf88746ee4e2a739185fc20d2d932654 Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Mon, 8 Jun 2026 21:19:52 +0000
Subject: [PATCH] Add a relative time option for time formatting, GitHub issue
 5009.

---
 format.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 tmux.1   | 10 ++++++++--
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/format.c b/format.c
index 7b184613..15afbe0b 100644
--- a/format.c
+++ b/format.c
@@ -117,6 +117,7 @@ format_job_cmp(struct format_job *fj1, struct format_job *fj2)
 #define FORMAT_NOT_NOT 0x100000
 #define FORMAT_REPEAT 0x200000
 #define FORMAT_QUOTE_ARGUMENTS 0x400000
+#define FORMAT_RELATIVE 0x800000
 
 /* Limit on recursion. */
 #define FORMAT_LOOP_LIMIT 100
@@ -4045,6 +4046,50 @@ format_pretty_time(time_t t, int seconds)
 	return (xstrdup(s));
 }
 
+/* Make a relative time. */
+static char *
+format_relative_time(time_t t)
+{
+	time_t	now, age;
+	u_int	d, h, m, s;
+	char	out[32], sign;
+
+	time(&now);
+	if (t == now)
+		return (xstrdup("0s"));
+	if (t > now) {
+		sign = '+';
+		age = t - now;
+	} else {
+		sign = '-';
+		age = now - t;
+	}
+
+	d = age / 86400;
+	h = (age % 86400) / 3600;
+	m = (age % 3600) / 60;
+	s = age % 60;
+
+	if (d != 0) {
+		if (h != 0)
+			xsnprintf(out, sizeof out, "%c%ud%uh", sign, d, h);
+		else
+			xsnprintf(out, sizeof out, "%c%ud", sign, d);
+	} else if (h != 0) {
+		if (m != 0)
+			xsnprintf(out, sizeof out, "%c%uh%um", sign, h, m);
+		else
+			xsnprintf(out, sizeof out, "%c%uh", sign, h);
+	} else if (m != 0) {
+		if (s != 0)
+			xsnprintf(out, sizeof out, "%c%um%us", sign, m, s);
+		else
+			xsnprintf(out, sizeof out, "%c%um", sign, m);
+	} else
+		xsnprintf(out, sizeof out, "%c%us", sign, s);
+	return (xstrdup(out));
+}
+
 /* Find a format entry. */
 static char *
 format_find(struct format_tree *ft, const char *key, int modifiers,
@@ -4126,7 +4171,9 @@ found:
 		}
 		if (t == 0)
 			return (NULL);
-		if (modifiers & FORMAT_PRETTY)
+		if (modifiers & FORMAT_RELATIVE)
+			found = format_relative_time(t);
+		else if (modifiers & FORMAT_PRETTY)
 			found = format_pretty_time(t, 0);
 		else {
 			if (time_format != NULL) {
@@ -5131,6 +5178,8 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 					break;
 				if (strchr(fm->argv[0], 'p') != NULL)
 					modifiers |= FORMAT_PRETTY;
+				else if (strchr(fm->argv[0], 'r') != NULL)
+					modifiers |= FORMAT_RELATIVE;
 				else if (fm->argc >= 2 &&
 				    strchr(fm->argv[0], 'f') != NULL) {
 					free(time_format);
diff --git a/tmux.1 b/tmux.1
index 130b8cf3..57746ac7 100644
--- a/tmux.1
+++ b/tmux.1
@@ -6323,9 +6323,15 @@ gives
 gives
 .Ql Sun Oct 25 09:25:02 2015 .
 Adding
-.Ql p (
-.Ql `t/p` )
+.Ql p
+.Pq Ql t/p
 will use shorter but less accurate time format for times in the past.
+.Ql r
+.Pq Ql t/r
+will show the time relative to the current time, for example
+.Ql \-1m
+or
+.Ql +2m23s .
 A custom format may be given using an
 .Ql f
 suffix (note that