How often does UPS packages arrive earlier than the scheduled delivery date?

just wondering. i have a package that had an arrival scan today at 4 o clock in san pablo, and i'm in san francisco..... is there a good or bad chance that it could possibly come tomorrow? the scheduled delivery date is monday the 18th....|||I don't think I have ever had a UPS package arrive early. Packages move through the UPS system in an orderly and planned way, so for something to come early would mean the system isn't working as expected.|||it could get here by tomorrow, i have a package scheduled for the 18th too and i checked the tracker for my package and it was in a ups center 40 minutes from my house at 8am and they sent it back out at 5pm so i'm pretty sure i'm getting it tomorrow so you might get yours too