Ahead of time

He navigated the course adeptly, having trained on it for months ahead of time.

But from Northallerton No. 46143 reached 65½ m.p.h. by Otterington, 73 by Thirsk, 79½ by Pilmoor, and 82½ by Alne and was still accelerating when it was decided on the footplate that the train was getting too much ahead of time—and no wonder, with 40 min. allowed for the level 30.0 miles from Northallerton to York!—so that the engine was drastically eased.

In the future, if you know that you're going to be mixing inviteds and uninviteds while out, call them all ahead of time to caution the inviteds against talking about the wedding and to tell the uninviteds about your guest list so they know you didn't forget about them […]