Brady and Sarah have been messaging on a site for a while now. The site tells you when you sent your messages; but not in exact detail.
For example, Sarah messaged Brady "What's up?" 2 hours and 31 min ago, however it only says "2 hours ago". But when Brady messaged Sarah "Hi!" 47 min ago it said "47 min ago".
(Once it passes the 1 hour mark it is then generalized to how many hours ago)
Brady sent Sarah an important message almost a day ago, he needs to know when, to the exact minute, he sent this. He needs this information very soon. But the site says "23 hours ago".
It's 4:16 PM right now, but for the next 2 days (beginning immediately), he'll have no source of time.
How can Brady find the exact time he sent this message, with the least amount of new messages?