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I have an excel spreadsheet containing a column of dates.

When data is copied from other spreadsheets into this spreadsheet the dates change and become inaccurate.

Changing the format of the problematic column from "date" to "number" reveals the data being copied across is correct. It turns out the new spreadsheet displays dates calculated from 1904-01-01 instead of 1901-01-01.

How do I remedy/prevent this?

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up vote 2 down vote accepted

Somewhere you have a Mac version of Excel involved. Its default start date (or at least an earlier version default is 1904)

You can change the date preferences in Mac Excel to start from 1900

Note Windows Excel dates are actually calculated from 1899-12-31 not 1900-01-01 as Excel copied Lotus 123 and the original programmers thought 1900 was a leap year.

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Thanks! That will help me avoid future problems but is there any way of changing the affected document? In particular is there any way of fixing it within a Windows version of Excel (I no longer have access to a Mac version) – trowel Nov 28 '10 at 21:30

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