https://github.com/djcb/mu/commit/0a4fabbf446d15b538600dfe7d879cad70ce941e

From 0a4fabbf446d15b538600dfe7d879cad70ce941e Mon Sep 17 00:00:00 2001
From: "Dirk-Jan C. Binnema" <djcb@djcbsoftware.nl>
Date: Sun, 28 Sep 2025 18:52:56 +0300
Subject: [PATCH] utils: avoid fmt:gmtime/fmt::localtime

They've been deprecated and give build warnings with new enough libfmt.
---
 lib/utils/mu-utils.hh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/utils/mu-utils.hh b/lib/utils/mu-utils.hh
index ecdc2f24d..32bb0ddb7 100644
--- a/lib/utils/mu-utils.hh
+++ b/lib/utils/mu-utils.hh
@@ -145,7 +145,9 @@ auto mu_join(Range&& range, std::string_view sepa) {
 template <typename T=::time_t>
 std::tm mu_time(T t={}, bool use_utc=false) {
 	::time_t tt{static_cast<::time_t>(t)};
-	return use_utc ? fmt::gmtime(tt) : fmt::localtime(tt);
+	std::tm time_tm = {};
+	use_utc ? gmtime_r(&tt, &time_tm) : localtime_r(&tt, &time_tm);
+	return time_tm;
 }
 
 using StringVec = std::vector<std::string>;