There has never been a button to insert the date/time on any toolbar. Do you
mean that the Date and Time command is missing from the Insert Menu? If so,
try Tools, Customize, Toolbars tab and press the REST button. Let us know if
that works.
There is actually an Insert Date button on the Header and Footer toolbar,
but, like you, I suspect the OP was talking about Insert | Date and Time,
and it could be that the cause is that described at http://sbarnhill.mvps.org/WordFAQs/LostSymbol.htm.
