The Year 2038 problem (also called Y2038 or Y2k38 or Unix Y2K) relates to representing time in many digital systems as the number of seconds passed since 00:00:00 UTC on 1 January 1970 and storing it as a signed 32-bit integer. Such implementations cannot encode times after 03:14:07 UTC on 19 January 2038.
Background for anyone who hasn't heard of this problem before: https://en.wikipedia.org/wiki/Year_2038_problem