it is documented, see here: https://pmg.proxmox.com/pmg-docs/api-viewer/index.html#/nodes/{node}/tracker/{id}I wish they would specify such details in the api documentation.
endtime: Only consider entries older than 'endtime' (unix epoch). This is set to '<start> + 1day' by default.
starttime: Only consider entries newer than 'starttime' (unix epoch). Default is 'now - 1day'.