Oh look, it's the 2038 problem in action! When you store time as a signed 32-bit integer, you're basically giving your system an expiration date of January 19, 2038. After that? Total digital apocalypse.
The poor guy is staring at a calendar showing both December 1901 and January 2038 because his phone just time-traveled to the edges of its numerical universe. When that integer counter maxes out, systems will wrap around to negative numbers—hello 1901, goodbye sanity!
Somewhere, a COBOL programmer is muttering "Y2K was just a practice round."