allow state transition timestamp to be bumped

[lblau]

I frequently got distracted and forgot to change the state of sessions/lunch/closing circle etc. whilst in the thick of it.

I'd really like to just be able to bump the timestamp on the state transition back by some relative amount (1 minute, 1 hour, etc.). That'd avoid any confusion with time zones.

Perhaps it isn't crucial that the data is accurate to the nanosecond but i'd rather be able to change it to at least be approximately correct.