How to date an early-2000s jersey

Nike made every Arsenal jersey of the era, so the sponsor dates it. Sega Dreamcast runs to the end of 2001/02, and O2 takes over from 2002/03.

Two switches inside three seasons. Sharp ended in 2000, so any Vodafone shirt is 2000/01 or later. Umbro made the shirt up to 2001/02, Nike from 2002/03.

Nothing changed on the print. Reebok made every one and Carlsberg sponsored every one, 2000/01 through 2004/05, so these are dated by the shirt itself rather than the badge or the sponsor.

Umbro throughout, so the sponsor splits the era in two. Autoglass ends with 2000/01, and Fly Emirates starts with 2001/02 and stays.

adidas made all of them, so the sponsor is the tell. Newcastle Brown Ale ended in 2000, NTL ran 2000/01 to 2002/03, and Northern Rock took over from 2003/04.

The maker and the sponsor changed together. adidas and Holsten to the end of 2001/02, then Kappa and Thomson from 2002/03 — one look tells you which half of the era you are holding.