To explain:
My slots were supposed to expire on August 7.
I purchased energy and extended them by exactly one year to August 2, 2017.
Do any bugs result from extending it to one year (such as having the expiry date in the same month but in a different year)?
Sorry for a semi-useless topic, but I'm slightly worried there might be a bug or unintentional behavior here.
No.
(Look up Unix time if you're curious why. Years, months, and days aren't represented at the server level.)