diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index 908999ab5f5d4..c52be81ca6ba1 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -558,6 +558,22 @@ inline void write_digit2_separated(char* buf, unsigned a, unsigned b,
   auto usep = static_cast<unsigned long long>(sep);
   // Add ASCII '0' to each digit byte and insert separators.
   digits |= 0x3030003030003030 | (usep << 16) | (usep << 40);
+#ifndef _WIN32
+#  if defined(__GNUC__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+  digits = __builtin_bswap64(digits);
+#  else
+  if (is_big_endian()) {
+    digits = ((digits & 0xff00000000000000ull) >> 56) |
+             ((digits & 0x00ff000000000000ull) >> 40) |
+             ((digits & 0x0000ff0000000000ull) >> 24) |
+             ((digits & 0x000000ff00000000ull) >> 8) |
+             ((digits & 0x00000000ff000000ull) << 8) |
+             ((digits & 0x0000000000ff0000ull) << 24) |
+             ((digits & 0x000000000000ff00ull) << 40) |
+             ((digits & 0x00000000000000ffull) << 56);
+  }
+#  endif
+#endif
   memcpy(buf, &digits, 8);
 }