Origin of saying 'Thank Buddha it's Tuesday'

What is the origin of the saying 'Thank Buddha it's Tuesday.'?

As @Juhasz suggests, it certainly sounds like a play on Thank God it's Friday. I don't doubt that for a moment. But the OP's impression that this is a commonly used saying made me want to find out more about it.

Thank God it's Friday, as most of us know, is an expression used by Western and other English speakers to express relief at the arrival of the weekend (Wikipedia). It's commonly abbreviated as TGIF.

As I expected, my search for Thank Buddha it's Tuesday turned up multiple references to Thank Buddha it's Friday. Here are examples:

• Hsi Fang Temple: a Friday evening event at a Buddhist Temple in San Diego (also on Facebook)
• Buddha's Light International Association: a Friday online book club
• Solid Threads Clothing: a T-shirt with the phrase, and a description that reads, "Sometimes you just want to thank someone other than God for the best day of the week. We thought Buddha seemed like a good guy to thank.."

Like Thank God it's Friday, Thank Buddha it's Friday has an abbreviation: TBIF. This abbreviation seems to have become part of internet slang (AcronymsandSlang.com and AllAcronyms.com).

Only one reference specifically to Thank Buddha it's Tuesday turned up in my search: a reference to an English-language site offering a series of meditation sessions scheduled on Tuesdays in April of 2017 on the Spanish Island of Ibiza (Rebeca Castella).

To sum all that up, Thank Buddha it's Friday seems to be a pretty commonly used expression, and appears to be a well-meaning, humorous play on Thank God it's Friday. Someone using Thank Buddha it's Tuesday is likely counting on sufficient use of Thank Buddha it's Friday to make this expression strike a chord and probably intends to attract people interested in Buddhism or Buddhism-inspired activities like yoga or meditation by using light-hearted humor.