Why is my Excel chart misbehaving?

[HigaDequasLuoff]

I'd normally see myself as an expert on Excel and am more usually answering these kinds of queries than answering them but I am stumped today.

Last time I had to do this chart, where the horizontal axis needs to be a date, this was just automatically recognised and I could select for the gridlines to be by month.

Today, it's refusing to register that I want months and is only offering the option to show axis markings in absolute values - obviously choosing 30/31 etc or any set number gets misaligned from the starts of the months very quickly.

I know this is possible but the online help pages that I get from googling for it start with saying to select the date axis option - and this simply isn't being shown for me.

It's not a version issue as I know I used this function on this same computer recently. I'm using Office 365.

Does anyone know what is going on and how to make it behave?

Pics - (1) screengrab of my options box
(2) What the options box should look like according to online help.

Are you able to show the underlying data?

ah ha - I have solved my own query - thanks for the response @SisyphusDad - I realised that the last time I used this feature, the data had sequential dates and no gaps of missing dates. The data this time didn't have every date represented so it was being treated like a scatter plot rather than a line graph. When I filled in the gaps so that each sequential date was there in the data, the option to display the axis as a proper date was suddenly there again.

I now have the happy of a well-behaved graph.

Don'cha jus luv Exel