I would like to know your perspective on the following:
We don’t really poskin that an early Maariv changes (and/or קבלת שבת) the date, do we? (Along the lines of a Terumas haDeshen, if I recall correctly.) There have been times when I have been surprised in both directions (when someone with a yahrzeit acts as if he is no longer a “chiyuv” for Maariv, even though the date hasn’t changed; as well as someone with a yahrzeit on the upcoming day treating the early Maariv as if it is already the next date). I would have thought that even though it is the next day’s Maariv, it isn’t really the next day, it is just that it is permissible to fulfill Tefillas Maariv before dark.
This past Erev Shabbos my father was planning on still saying kaddish at the early Maäriv minyan – since even though it is Maariv, it was still 23 Tammuz and not yet the next date. And yet someone else in the community who plans on early (between plag & shkia) Shabbos this week, assumes that his 2 Av yahrzeit starts at קבלת שבת, even though before shkia it is still Rosh Chodesh Av.
Thank you, Kol Tuv, etc.
Rav Gad Ifrah said for most things yes, the Maariv actually changes the date.