The 30-day period starts at midnight eastern time. Note that the key stated rule is that, to have points returned to your account without penalty, requires you to make the change 31 or more days out, and that 31st day ends at midnight . One should avoid waiting until the last minute to make any change that could leave points open to being put into holding. You cannot call MS late in the evening at 31 days out to make a change because MS is closed. If you go online late in the evening, the online system may not be working properly (a common occurrence), the online system may be down for maintenance, your computer may not be working properly, a storm may shut down electricity in your area. In other words, the longer you wait on that 31st day, the greater the probability of failure.