Wierd Formula hidden somewhere in data base

I have large database ( 190,000 rows of data and 7 columns). During one of my analysis, I deleted all data from 12/18/2015 throu 12/31/2015. Which left a data base of all months and all dates up to 12/17/2015.

After I finished what I was doing, I closed the database. When I reopened it, all dates are there, which I expected to see. But when I run a query using a different file and input all the data with all the dates, it picks up all data from 1/1/2015 to 12/17/2015?

I do not see any thing to account for this in the data fields of either the original database or the query field from another file. But something is stuck with data above 12/17/2015.

Can someone give me some ideas of where to look or what to do. I have already copied the original database into a new file and saved it. But it persists. Therefore somehow I must have used the query file to delete all dates past 12/17/2015. But I don't see anything in the query file that could account for this. So, I am looking for help. Thanks

found the problem

Two things. I had copied and pasted some data into my analysis program, by using "Insert Function" . This removed some of my "IF= etc" formulas by using the Insert Function. Should have used Insert Function only for the row/columns I was going to put new data in and not the entire row from A1 to ZZ or however far that row goes in Excel. Lesson learned. "When doing things too fast to try to save time, sometimes it causes you many times that time to figure what happened why it didn't work".