Screwy dates

[BasicGuy]

I am having trouble with date formats. The list below shows a column of dates. They all have the same date format. They should all read 2012-06-15 though -22.

2012-06-15 14:00:00
2012-06-16
12/30/99 12:00 AM
2012-06-18
2012-06-19
2012-06-20
2012-06-21
2012-06-22

These are all references to a date cell in external files. For example, the 12/30/99 entry comes from /user/folder / 5min Data 6-17-12.ods'#$1Graph.$C$30. All the rest have identical addresses with only the day difference - from 15 to 22.

The date format is Date: 12/31/99 for all of them.

How do I get this thing working correctly?

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Second problem. I open a spread sheet containing dates (as above) and all the dates have changed from YY= 12 to YY = 07 or 08. I can't change them to the right value except by typing them in again (290 entries x 15 files).

Thanks