The timestamp of the first tick is 1660052760, you can’t request a range starting earlier than this nor request timestamps in the future.
Btw, make sure you read this, especially point 18 https://forum.dfinity.org/t/upcoming-icpcoins-neutrinite-sns-decentralization/25308/10?u=infu
Also, while the architecture and interfaces right now get the job done for our use cases of displaying market data and carried us so far, they may get changed in the future. We will try to keep interfaces fixed and working as long as possible. But it’s safe to say the alternative - getting data directly from DEXs isn’t more stable. Our adapters usually require changes & modifications every month. Once we create standards, the whole system will become more resilient and backwards-compatible.