file1.txt:

2009/01/01 00:05:00.000  nmbr nmbr
2009/01/01 00:10:00.000  nmbr nmbr
2009/01/01 00:15:00.000  nmbr nmbr
2009/01/01 00:20:00.000  nmbr nmbr

file2.txt:

2009/01/01 00:00:00.000  nmbr nmbr
2009/01/01 00:05:00.000  nmbr nmbr
2009/01/01 00:10:00.000  nmbr nmbr
2009/01/01 00:15:00.000  nmbr nmbr
2009/01/01 00:20:00.000  nmbr nmbr