Cancel sniping, at your convenience
The only calculations you are ever going to need to make are the amount of time left until noble train lands, divided in half.
Generally, I will use whole minutes, or half minutes. So if noble train lands in 20 minutes, I'll wait until 18 minutes (I also prefer the even minutes if I can choose to be picky), I'll likely send at 18 minutes or wait until 10 minutes (As there's less time until you have to cancel it, don't have to sit around and wait nearly as long)
Thus if I send 10 minutes from when the noble train lands, all I have to calculate is Noble train lands at 7:47:29:190, 7:47:29:290, 7:47:29:390, 7:47:29:490, I would want to send my attack at a barb at 7:47:19:189 (Or whatever ms you can manage) and cancel at 7:42:29 (The ms on the cancel doesn't matter, as long as the cancel happens WITHIN the same second, it will return at the precise ms that you sent the attack at) thus the attack sent ms is what time the attack returns.)You can sit and try to send attacks at intervals of 30-60 seconds, without much calculations as you are literally just dividing it in half, and have as many tries to get the proper ms as you have time until the noble train lands.
Sending at 18 minutes means canceling at 9 minutes.
Sending at 16:30 minutes until train lands means canceling at 8:15.
10:20 means canceling at 5:10. Do your best to avoid odd seconds as that means canceling at an odd second which can feel confusing. Canceling at a 0 second is generally easiest.
10 minutes is my go to time to send, with 5 minutes as the cancel time.
