Add ChangeLog entry for use of gmtime
@@ -5,6 +5,8 @@ mbed TLS ChangeLog (Sorted per branch, date)
Bugfix
* Fixes an issue with MBEDTLS_CHACHAPOLY_C which would not compile if
MBEDTLS_ARC4_C and MBEDTLS_CIPHER_NULL_CIPHER weren't also defined. #1890
+ * Fix build failures on where only gmtime() is available but neither
+ gmtime_r() nor gmtime_s() are present. Fixes #1907.
= mbed TLS 2.12.0 branch released 2018-07-25
