T0的定义在WHO稳定性测试指南有明确的规定，指放入箱体进行稳定性考察的日期，如果三批一并放入，相隔时间较久，问题在于T0的测试结果是否有代表性，要考虑最大允许的时间，按照经验，一般情况下一个月是允许的；如果三批在放入前一并测试一次，风险是用户承担，对于稳定性考察是相对差的条件。
https://lib.shilinx.com/wiki/index.php?title=WHO_ECSPP_TRS_1010_Annex_10_Stability_testing_of_active_pharmaceutical_ingredients_and_finished_pharmaceutical_products_201805&searchText=WHO%20stability
The initial date of storage should be considered t0 and stability time points should be defined as a date with respect to t0. For example, if t0 is 1 January 2020 then the one-month time point corresponds to either 1 February or 31 January 2020. For each time point, samples should be withdrawn and tested as per the protocol. Testing should be completed as soon as possible. Deviations from the protocol should be recorded and justified.