The interfaces in time.h are inconsistent, partially underspecified, subject to undetectable overflow, not thread-safe and present security issues. Along the lines of ISO 9945 (POSIX), we propose to modernize the interfaces to avoid these problems. Changes in v2-properly distinguish calendar time and elapsed time-the _r functions are not reentrant and may have races if the time environment is changed-avoid to use the tm buffer where it is not allowed-define offset macros for the tm structure-relate the monotonic clock to system suspension-change from pointer to array notation-better explanation why overflow of clock values is a user space problem