Das Lakshan Parva (the 10-day Das Lakshan) for Digambar Jains in 2025 begins on 29 August 2025 and runs for 10 days, ending on 7 September 2025. Kshamavani (forgiveness day) is typically observed a bit after this period, around 8 September 2025, depending on local practice. You asked for the first day, so that is 29 August 2025. You can read more here