import core.time : msecs, usecs, hnsecs;
import std.datetime.date : DateTime;

assert(SysTime(DateTime(1999, 1, 6, 0, 0, 0)).endOfMonth ==
       SysTime(DateTime(1999, 1, 31, 23, 59, 59), hnsecs(9_999_999)));

assert(SysTime(DateTime(1999, 2, 7, 19, 30, 0), msecs(24)).endOfMonth ==
       SysTime(DateTime(1999, 2, 28, 23, 59, 59), hnsecs(9_999_999)));

assert(SysTime(DateTime(2000, 2, 7, 5, 12, 27), usecs(5203)).endOfMonth ==
       SysTime(DateTime(2000, 2, 29, 23, 59, 59), hnsecs(9_999_999)));

assert(SysTime(DateTime(2000, 6, 4, 12, 22, 9), hnsecs(12345)).endOfMonth ==
       SysTime(DateTime(2000, 6, 30, 23, 59, 59), hnsecs(9_999_999)));