Stellar does a reset/cleaning of its testnet to the genesis block once per quarter to keep down spam for general efficiency and maintenance best practices. The first reset was done on January 30th, 2019. Be aware and plan accordingly.
To preserve a good experience for developers, the SDF testnet is periodically reset to the genesis (initial) ledger. This ensures the removal of spam, minimizing the time to catch up to the latest ledger, and easier system maintenance over time.
When this happens, all ledger entries (such as accounts, trustlines, offers, etc.), transactions, and historical data are cleared for both Stellar Core and Horizon.
As a result, developers should not rely on the existence of any accounts or the state of any balances within the testnet.
Since January 2019, the testnet has been reset once per quarter (every three months):
SDF will announce the exact date with at least two weeks' notice on the Stellar Dashboard and several of Stellar’s online developer communities.
Updated 10 days ago