It’s my Hebrew birthday (tonight/tomorrow), and I’d like to finish the whole Sefer Tehillim over the 25 hours. I won’t have enough time to do it during the day, tomorrow, however… can I say some of the prakim tonight so that I’ll be able to finish the whole thing by nightfall tomorrow?
You may say the tehillim, even though it is at night.
Thee are a few reasons given for this. First of all it isn’t prohibited to say it at night, it is only a preference to say it instead by day, but obviously if it can’t be done by day it is also alright at night. Even for those who are on the level of doing things according to kabalah, it is only for the very pious, and not for regular people.
There are many of the opinion that not saying Torah S’bksav at night doesn’t apply to tehillim.
Others say that the Arizal was only referring to learning, and not when it is being said as a prayer or segulah, such as in your case.
Besides, happy birthday, and may H-shem grant you many happy long years!
M:B Shar Hatzion 238-1, Eshel Avraham (Butchatch) O:CH 238, Btzel Hachochma 4-45, Kikar Laden (Chida) 5-7. Orchos Rabeinu 1 pg. 97