Match dates in two colums, then insert value next to matched date

[sipa]

I have two columns of dates, these are in a random order in C2. In E2 the dates are in sequence.

The dates in C2 may or may not exist in E2, and there maybe blank cells interspersed in Column C.

I've been trying to achieve this with index/match but just can't get it to work.

If the date is found in Col C & E, place a value from A1 next to the date in Col E.

Any help appreciated.

Thanks

Edit : The dates in column C may occur more than once, but only once in Col E

[alansidman]

Attach a sample workbook. Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.

Remember to desensitize the data.

Click on GO ADVANCED and use the paperclip icon to open the upload window.

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[sipa]

As requested Sample workbook uploaded

thank you

[sipa]

Here is an update.

I now have the columns matching the dates using this index match formula : =IF('GP'!M18="","",INDEX('GP'!M18:'GP'!M301,MATCH(B3,B3:B197,0)))

My new question related to my earlier post, is how can I replace the returned date with "MN" ?
Can anyone offer any help please