Showing date and time properly on plots

Hello everyone,
I'm trying to plot time series. I combined date column and time column to have both in each cell. Now when I choose the scatter plot it just shows the numbers instead of date. I tried several things such as changing the format before (number or text) and after plotting and (custom) and ...
The only way that worked is choosing each cell and push enter bottom, then it changes the appearance a little and shows that properly but I can't do this for 36000 line of data
Would you please help me with this problem?
Thanks.

Click on your graph, then position the mouse cursor over the axis that you want to change and right-click. On the pop-up dialogue box you will see an option to Format Axis, and this will allow you to apply the format you wish to see (maybe "Linked to Source").

Hope this helps.

Pete

Thanks Pete for your suggestion. I tried it and it didn't work.

Thanks, MrShorty. You are right. They were text, so I could convert them to the correct format by =Datevalue(text)+timevalue(text)
function. Thanks a lot for your help