Learn English – Appropriate preposition in “your preference of/for time and venue”

From my experience, "COB" is a commonly used acronym to express delivery of a project or task by the end of business on a certain day. EDIT: You would only ever write this, not say it out loud to a colleague.

"I will make sure to send you that spreadsheet by COB Thursday."

I have rarely encountered the construction "end of _" in that context. I usually see it as "EOM" or "EOY" in financial or management reports.

If you're looking for something to use in everyday language with your co-workers, mplungjan's "It's curtains for me" or a phrase like "I'm throwing in the towel for today" is appropriate. Saying "It's COB for me" would sound weird.

In that sense, you can use 'by' with any tense. Consider its meaning as given by the Longman dictionary:

Before or not later than a particular time.

Examples:

• The document needs to be ready by next Friday.
• By the end of the day we had sold over 2000 tickets.
• By the time we got home we were tired and hungry.
• I'll be home by 9:30.
• Please try to have this done by Friday.

All the examples are borrowed from the Longman dict. so you can trust them.