I understand that the starting date to say "Veten Tal Umatar" during weekday AMidah outside of Israel is based on being 60 days after Tekufat Tishrei. This is always a solar-based calculation, and on the Gregorian calendar it occurs on Dec. 4 or 5th, currently.
If the starting time i sbased on a solar date, shouldn't we begin saying this when that solar date occurs, namely during shacharit or by davening Ma'ariv after 12 midnight when that solar date has occurred? It seems that if we start saying during Ma'ariv, we are a solar date too early.