# 420

> 420 is cannabis culture shorthand for cannabis itself and for April 20, celebrated as an unofficial cannabis day.

- Canonical: https://genetixbay.com/knowledge/glossary/420.html
- Also written: 4/20, four-twenty, 4:20, April 20, 420 friendly
- Glossary category: Grower slang and culture
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

420 (four-twenty) is a code word for cannabis and for the date 20 April (4/20 in US date format), observed in many countries as an informal cannabis holiday. "420 friendly" in a listing means cannabis use is accepted.

## In practice

The most widely cited origin is a group of California high-school students in the early 1970s who met at 4:20 pm to smoke, with the phrase spread later through music and fan culture. Other popular explanations, such as a police code or the number of chemicals in cannabis, are myths.

For growers, the date is also a calendar marker: in the Northern Hemisphere, mid to late April is a common time to start seeds for an outdoor season. GenetixBay itself launches its community on 20 April 2027.

## Don't confuse with

- **Croptober**: harvest season for outdoor growers in the Northern Hemisphere, around October.

## Related terms

[Marijuana](https://genetixbay.com/knowledge/glossary/marijuana.md), [Heady](https://genetixbay.com/knowledge/glossary/heady.md), [Connoisseur](https://genetixbay.com/knowledge/glossary/connoisseur.md)