Drip based on Day of the Week

S2Member seems to have a drip short code for number of days since membership was created: https://s2member.com/kb-article/s2drip-shortcode/ but it does not seem to have a way to drip based on first Monday, every Sunday, etc. What would the code be/ what PHP could be used to make this possible?

Thanks so much!
Best wishes,
Rosi

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