The streak feature was introduced on September 28, 2023. Assuming you started your streak on that date and extend it every day:
1,000 days - June 23, 2026
2,000 days - March 19, 2029
3,000 days - December 14, 2031
4,000 days - September 9, 2034
5,000 days - June 5, 2037
9,000 days - May 18, 2048
10,000 days - February 12, 2051
15,000 days - October 21, 2064
20,000 days - June 30, 2078
So September 28th 2022 is the earliest possible streak start