I'd say the Saturday after the paycheck closest to the 15th. People on bi-weekly pay schedules have funds again and it's counter cyclical to the 'Who's Hiring' threads.

The list of bi-weekly paychecks for 2020 is here: https://www.nfc.usda.gov/Publications/Forms/1217n_20.pdf

Meaning that June's thread should be on the 20th. July on the 18th. August on the 15th. September on the 12th. October on the 10th.

Second or third Sunday, evening.

Sunday might be good because then the question "what are you working on" is associated with what you might be working on over the weekend, i.e. things you're doing for curiosity, fun, or obsession, rather than a workaday job.