While most developers may dislike the imperial calendar, all of my bank/brokerage statements display dates using it, as do tax/pension forms. It's definitely still in heavy use for some very important data.
On a similar note, I recently requested a list of historical transactions from a brokerage and found that transaction dates continued to be annotated as Heisei all the way through Heisei 36 (2024), a full 5 years after Heisei officially ended in Heisei 31 / Reiwa 1 (2019). Late in 2024, transactions finally started being annotated Reiwa 6.
On a similar note, I recently requested a list of historical transactions from a brokerage and found that transaction dates continued to be annotated as Heisei all the way through Heisei 36 (2024), a full 5 years after Heisei officially ended in Heisei 31 / Reiwa 1 (2019). Late in 2024, transactions finally started being annotated Reiwa 6.