One should realise that absolute measurements do not exist (yet?). Our knowldge of physics just does not allow this (Planck, Heisenberg).
Have a look at the shortest possible time-step, it is in the region of 10 to the power of -44 seconds.
Which is way beyond our, NIST's and BIPM's capabilities.
Use measuring equipment to measure to the accuracy level you require and forget to create your own calibration lab. It just requires too much labour and capital for all practicle purposes.
Unless of course your happiness level can not be satisfied otherwise.
And stay away from believing. Thinking seems to me a better approach.
Measuring involves knowledge and experience on the following subjects: accuracy, uncertainty, repeatability, resolution, traceability, error, type of error, shannon criteria, sampling type, data processing, traceability to standards, etc., etc.
Cailibrating your equipment costs money. You have to pay for this, either by using a calibration lab or setting up your own calibration lab. Or just have fun getting into it as deep as your practicle knowledge and requirements allow.
Have fun, Frans