Asking your Bridesmaids

I would say same day! If you ask one now and don't ask the other until later and they are close, then someone could feel left out.

I would ask them all around the same time so word doesn't get out that some have been asked and others haven't. But I would also wait until at least 9-12 months until your wedding before asking anyone.

Ask them all at the same time. It will make it easier and make sure there are no hurt feelings if you ask one before the rest. Especially if they talk to one another and find out one was asked but not the rest.

I agree there is likely less chance of hurt feelings if you ask them all in the same timeframe, but I would ask each individually -- not as a group -- in case someone has to decline. A "public ask" can put unnecessary pressure on someone who might prefer to attend as a guest feeling like they have to say "yes." Also, I agree with pp about waiting to ask anyone until you're under a year; so much can change, even with family members (e.g., pregnancies, divorces, relocations, etc.). There is no downside to waiting until you are much closer to the wedding.

Same day! That way they all know.

If it's convenient for you to do the same day, that would be super cute

Ask them all at the same time. Good luck!