Quite a few people got caught out today as yesterday immigration offices were closed (not sure if all) for the Royal Ploughing Ceremony.
They were given overstay stamps as their entry stamp expired yesterday.
When giving extensions for tourist or exempt entries all offices will allow you to go at least 7 days prior to your stamp expiration. Most will allow 30 days and some even 45 days prior.
They add on the days so there is no downside to going early.
Don’t leave it until the last day if you can help it. You could be caught out not realising it’s a holiday (or even the weekend).
*Caveat. If you are changing the reason for an extension like marriage to retirement or tourist to retirement they’ll date it from the day you apply so you will loose the remaining days.