Updating holiday planner for this year?

I know you've provided a link to a sample file, but please upload it here rather than google - many members can't get to google files due to company firewalls, etc. The same applies to .png pictures, which many members can't see. To upload a file here, click 'Go Advanced' then scroll down to 'Manage Attachments'.
Once you've done this, I'm sure one of us will be able to help.

Also, please don't use such large text in future - just leave it at the default size.

OK I made it hard for myself. Hope someone can help me change the dates on the attached overview to Oct 16-Sep 17 populated from the monthly tabs? Many thanks :-)

Okay, maybe I'm missing something, but whoever set this up in the first place has linked it all together already. All you need to do to change the year is change it in L1 on the Overview tab. The dates fill in automatically on each tab from this. The only manual changes to do (apart from that) are in the title 'Holiday Planner - (Year 2015/16)' and in F3. You could use these formula in A1 and F3 to make them automatic as well but it may not be worth it for the sake of two cells:

Formula:

="Holiday Planner - (Year "&L1&"/"&RIGHT(L1,2)+1&")"

=L1&"/"&RIGHT(L1,2)+1&" Entitlement"

That's assuming that you want to start with a blank slate for this year, filling in things like 'Carry Forward' manually. If you want them to come automatically from the already-existing 2015/16 file, that would mean having some formulae in column D which refer to column H in the previous year's file.
(If you're not doing this, then you can clear the data (all the '1's) from the monthly sheets together by grouping the tabs (left-click 'Oct', hold 'Shift' then click 'Sep'), select the range F1:BO31 then hit 'Delete' to clear all the sheets simultaneously, leaving you with just the 'Holiday Entitlement' and 'Carry Forward' (columns C and D of 'Overview') needing clearing/checking.)

Is there something I'm missing?

Originally Posted by colgor

Selecting tabs is easy enough but how does one select the range without unselecting the tabs?

Select the multiple tabs you want. They'll all be highlighted (normally white instead of grey in 2010 - not sure about 2013). Now select the range you want - it'll be selected on all the active sheets. Do what you need to do, then click any non-selected tab to get out of the multiple-sheet-selection (if you've selected all your sheets, then just click any sheet tab apart from the one in the foreground.
Since a picture is worth a thousand words: the pic below shows Sheets 1, 2 and 3 selected, Sheet 4 not selected. To get back to having only a single sheet selected in this case, you'd click the Sheet 4 tab. If Sheet 4 wasn't there, clicking either Sheet 2 or 3 would get out of multiple-sheet-selection (because Sheet 1 is in the foreground sheet - shown by the text in the tab being bold).
Excel-multiple-sheet-selection.jpg
With multiple sheets selected, anything you do in a cell or range will be done on all the sheets. Try it with a blank file - select two or more sheets, then put a number or text into a cell - you'll find that your entry has appeared on all the sheets you had selected.

Hope that helps.