Bitstamp are phasing out their old csv format of transaction history (currently both can still be generated, but the website mentions the old format will be phased out)
Updated CSV format
In December 2023, we upgraded the CSV file format for transaction exports to comply with the RFC 4180 standard, ensuring improved data consistency and compatibility. To generate CSV files in the previous format, you can select "Old format" during the export process. However, please be aware that this option will be removed in the coming months.
Bitstamp are phasing out their old csv format of transaction history (currently both can still be generated, but the website mentions the old format will be phased out)