# First day (of validity)

> first day on which a stamp is valid or a special postmark is used

**Wikidata**: [Q1362379](https://www.wikidata.org/wiki/Q1362379)  
**Source**: https://4ort.xyz/entity/first-day-of-validity-


## References

1. Lexikon der Philatelie (5 ed.)
2. Großes Lexikon der Philatelie (2 ed.)