Have you ever wondered why Indian telecom operators offer their services with a 28-day validity instead of the more conventional 30 days? Here is the trick: We pay for 13-months instead of 12-months This is how it happens, by paying for 28 days, the telecom operator gets 2-days/month more. Let's break down the math: This is 24-days in a year. Now, a total of 7-months have 31 days, which makes it 31-days in a year. Even if we subtract 2 days of February, the count comes down to 29-days, which is ~1 month more. This means that with the 28-day billing cycle, telecom operators effectively gain 29 extra days in a year compared to a traditional 12-month billing cycle with 30-day periods. These additional days represent nearly one extra month of revenue for the telecom companies, making it a lucrative strategy for them.