diff --git a/format.c b/format.c
index 8953f65d2..a911fed59 100644
--- a/format.c
+++ b/format.c
@@ -127,6 +127,7 @@ format_job_cmp(struct format_job *fj1, struct format_job *fj2)
 #define FORMAT_QUOTE_SHELL_SQ 0x20000000
 #define FORMAT_OPTIONS 0x40000000
 #define FORMAT_ENVIRON 0x80000000ULL
+#define FORMAT_DIFFERENCE 0x100000000ULL
 
 /* Limit on recursion. */
 #define FORMAT_LOOP_LIMIT 100
@@ -4221,6 +4222,17 @@ format_relative_time(time_t t)
 	return (xstrdup(out));
 }
 
+/* Make a time difference in seconds. */
+static char *
+format_time_difference(time_t t)
+{
+	time_t	 now = time(NULL);
+	char	*out;
+
+	xasprintf(&out, "%ld", (long)now - (long)t);
+	return (out);
+}
+
 /* Find a format entry. */
 static char *
 format_find(struct format_tree *ft, const char *key, uint64_t modifiers,
@@ -4305,6 +4317,8 @@ found:
 			return (NULL);
 		if (modifiers & FORMAT_RELATIVE)
 			found = format_relative_time(t);
+		else if (modifiers & FORMAT_DIFFERENCE)
+			found = format_time_difference(t);
 		else if (modifiers & FORMAT_PRETTY)
 			found = format_pretty_time(t, 0);
 		else {
@@ -5684,6 +5698,8 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 					modifiers |= FORMAT_PRETTY;
 				else if (strchr(fm->argv[0], 'r') != NULL)
 					modifiers |= FORMAT_RELATIVE;
+				else if (strchr(fm->argv[0], 'd') != NULL)
+					modifiers |= FORMAT_DIFFERENCE;
 				else if (fm->argc >= 2 &&
 				    strchr(fm->argv[0], 'f') != NULL) {
 					free(time_format);
diff --git a/tmux.1 b/tmux.1
index b9cfae3e7..69d3f86aa 100644
--- a/tmux.1
+++ b/tmux.1
@@ -6815,10 +6815,14 @@ Adding
 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
+will give the time relative to the current time, for example
 .Ql \&1m
 or
 .Ql 2m23s .
+.Ql d
+.Pq Ql t/d
+will give the difference from the time to current time in seconds (future
+times are negative).
 A custom format may be given using an
 .Ql f
 suffix (note that