Passage: The changeover period during which the former currencies' notes and coins were exchanged for those of the euro lasted about two months, until 28 February 2002. The official date on which the national currencies ceased to be legal tender varied from member state to member state. The earliest date was in Germany, where the mark officially ceased to be legal tender on 31 December 2001, though the exchange period lasted for two months more. Even after the old currencies ceased to be legal tender, they continued to be accepted by national central banks for periods ranging from several years to indefinitely (the latter for Austria, Germany, Ireland, Estonia and Latvia in banknotes and coins, and for Belgium, Luxembourg, Slovenia and Slovakia in banknotes only). The earliest coins to become non-convertible were the Portuguese escudos, which ceased to have monetary value after 31 December 2002, although banknotes remain exchangeable until 2022.

Question: How long did the changeover period last?
two months