I created a file on 2/7/2015. I searched SharePoint using "Write=2/7/2015" and could not find the file! When I found it by keywords, search said it was created on 2/7/2015.
The library said it was created on 2/7/2015.
When I searched using "Write=2/8/2015" I found it!
Turns out that search works in a different time zone! Here's the quote from this MSDN article:
"All date/time values must be specified according to the UTC (Coordinated Universal Time), also known as GMT (Greenwich Mean Time) time zone."
My testing is in Eastern Standard Time (EST), so GMT is currently 5 hours "in the future". When using GMT my file was created at 2/8/2015 12:50 AM.
Now try to explain that to all of your SharePoint users!
By the way… what time zone are you, or your users using? In my Office 365 subscription it's defaulting to PST when I create new site collections. I guess I should go check all of my other site collections and see I remembered to change to them all to EST when I created them!