As the documentation there are two plans:
Clients of the standard plan:
There are 2,500 free requests per day, a combination of client-side and server-side requests; Every 1000 additional requests are charged a fee of $0.50 USD. It has a limit of 100,000 daily requests.
Google Maps API Premium Plan Customers:
Free shared daily quota of 100,000 requests per 24 hours; Additional requests applied against the annual purchase of Google Maps Apis Credits.
Google provides a virtual calculator for credit purchase simulation: Link to Calculator.
Google provides a monitor for API usage
Regarding time zone: There is no specific time zone for use and renewal is always done at midnight Pacific Time (PST - Pacific Standard Time UTC-8). "I believe it is 5 hours less than Brasilia"
Depending on what you use, 25000 is the use of basic maps, some Apis have a limit of 2500 calls per day as per documentation
– Leandro Godoy Rosa
As I said, I only use javascript: Maps, autocomplete.
– N. Dias