Unix timestamps cause a barrel of fun when leap seconds roll around.  See e.g. <a href="https:&#x2F;&#x2F;access.redhat.com&#x2F;articles&#x2F;15145#known" rel="nofollow">https:&#x2F;&#x2F;access.redhat.com&#x2F;articles&#x2F;15145#known</a><p>Trivia: &quot;Unix time&quot; is not seconds since midnight January 1, 1970 UTC.  It in fact represents the number of full days since January 1, 1972 UTC, plus 730, times 86400, plus the number of seconds since midnight.  Due to this definition, it is not monotonic, as it may occasionally have discontinuities of 1 second (in either direction!) due to leap seconds.<p>Best is to just count seconds since some epoch (e.g. Unix time based on TAI rather than UTC), but not many systems actually do this.