Linux, like a unix machine, counts time as the number of elapsed seconds since jan 1st, 1970, in coordinated universal time (UTC).
Then users can shift this UTC date/time to their own time zone, because everybody doesn't live in Greenwich, London. (https://en.wikipedia.org/wiki/List_of_UTC_time_offsets
Your machine shows an inaccurate UTC date. Normally this is taken care of automatically by the NTP protocol.
The Pi is a little special in that it doesn't keep track of time that passes when it is powered down (there is no battery backed RTC unit.)
It could take a little while for the machine to sync to the correct UTC date after bootup.
There are quite a few threads on the forum related to NTP and timekeeping. I would advise patience first, and dig into these topics only if time doesn't get accurate after a few days of uptime. (Or use the recipe posted by RaTTus above to accelerate the process)