Is 4:20 a national holiday?

4/20 is not a national or official holiday.

There are a few but not many I put bold the most important ones

It's the national 110th day of the year (only 255 to go)

It's Adolf Hitlers 129th birthday

It's National Pot smokers day

It's Chinese language day

It's Lima bean respect day

It's national cheddar fries day

It's national look alike day

It's national pineapple upside down cake day

It's Volunteer recognition day