From 7a33f5e78316f6740879767207cbb6a982b48ffc Mon Sep 17 00:00:00 2001
From: Filip Brcic <brcha@yandex.com>
Date: Tue, 18 May 2021 21:59:52 +0200
Subject: [PATCH] Handle subsecond time before epoch start correctly

---
 include/fmt/chrono.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index a8a619f7..85d152f0 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -414,10 +414,12 @@ struct formatter<std::chrono::time_point<std::chrono::system_clock, std::chrono:
     std::tm time = localtime(val);
     auto epoch = val.time_since_epoch();
     auto seconds = std::chrono::duration_cast<std::chrono::seconds>(epoch);
-    // auto subseconds = abs(std::chrono::duration_cast<std::chrono::duration<Rep, Period>>(epoch - seconds));
     auto subseconds = std::chrono::duration_cast<std::chrono::duration<Rep, Period>>(epoch - seconds);
 
-    if (subseconds < subseconds.zero()) subseconds = -subseconds;
+    if (subseconds < subseconds.zero()) {
+      time = localtime(val - std::chrono::seconds{1});
+      subseconds = std::chrono::seconds{1} + subseconds;
+    }
 
     if (subseconds.count() > 0) {
       auto width = std::to_string(Period::den).size() - 1;