narita express 14 days valid ticket

Hello everyone, i have a little question about the narita express that i can't find,
In january i'll be in tokyo for my first time, i booked an house in shibuya and i stay from 11th january till 25th january, i want to take narita express from narita to shibuya but i know the price of 4000 yen round ticket is possiblr only if you spend the ticket for the return 14 days after the arrival and unlucky my stay is 15 days, but the 14 days are counted from the hour you using the ticket or by the day?
I explain better:
If i use my ticket on the 11th around 15.00 pm it is counted for the whole day or the whole day is after 24h hours of the use?
Because if is like that on the 25th before 15.00 p.m i still use it?
Hope i explain it well
Thanks in advance

It's on a calendar day basis, so the 11th is day one and the 24th is day 14. You won't be able to use it on the 25th.

Yep, calendar days. There is no provision for the hour of use to be applied.