0-day 

1) warez obtained on the day of, or slightly before, its official (legal) release.
2) Information that is not publicly available until it is rapidly disseminated in the online community. Often contains the details of new computer vulnerabilities, allowing exploiters to comprimise computer networks before system administrators have a chance to secure their networks.

Dude, do you have access to any 0-day? I need to get my hands on the new version of Windows.

0-day by Evan B March 14, 2005

ARMY Independence Day

The day when BTS fans, ARMY, broke free from the toxic KPOP world.
Day: October 14
Motto: Borahae (I purple you, a saying Taehyung coined)
National Anthem: Make It Right

It's ARMY Independence Day, today. Alexa, play Make it Right by BTW

ARMY Independence Day by Grandpa Yoongi October 24, 2019

red letter day

a memorably happy or noteworthy day

When Jack comes home from his tour of duty, that'll be a red-letter day.

red letter day by johnpqrtst August 3, 2005

one day flu 

Excuse to miss school for an event.

Man mom i have the one day flu.

one day flu by Orgasmic Velociraptor December 12, 2016

Black Solidarity Day 

A memorial day, created in 1969 by Panamanian-born activist, historian, and playwright, Carlos E. Russell. It is annually observed the day before Election Day in November, the first Monday of the month. Its purpose is for African diasporic people to exercise a 24- hour moratorium from shopping or participating in other commercial activity such as using the transit system. You can only spend money at Black owned businesses. The Pan-African ideal of the observance is to highlight racial inequality and the gap between the wealthiest of one of the most powerful nations in the world and those living in poverty.

"I'm telling everyone in my family not to spend one dime on Black Solidarity Day."

Black Solidarity Day by IBTAL October 28, 2019

National Lesbian day 

EVERY DAY IS NATIONAL LESBIAN DAY, SAY IT WITH ME SEXUALITY ISN'T A CHOICE BE YOU AND BE PROUD!

Oh, today is national lesbian day, I'm excited for tomorrows national lesbian day

National Lesbian day by Just a lesbian October 24, 2020

Delete meme dump day 

December 17 is the day of delete meme dump day

On this day all mods are allowed to delete meme dump
This allows the mods to relax as the would not have to deal with meme dump

Memetastic discord mod: Yooo it's delete meme dump day!
Memetastic: Yes.

Delete meme dump day by Shitposter69420 December 11, 2020