Starting from year 1 they have sometimes missed ticks. Just because you didn't notice doesn't mean it didn't happen. First occasion summer of 2015, a whole days worth of exploration stats were never counted for. An occasion which FD admitted at the time, and customer support replied they're sorry but it's possible the stats would never get fixed, and they never did.
Anyways, this is not a problem of mine at this moment. A word of advice is not to care about the stats as much as they should be cared about.