I have set up a Jotform to expire at 23.59. Can you tell me is this time set to Australian Eastern Standard Time?

It follows the US Eastern Standard Time (server time, not your computer time).

You can also find that information in this link How-to-Limit-Submissions-in-a-Form

If you need to have control over the time, based on your own timezone, you can use conditions as a workaround. We also have a very detailed guide about this on the link below.

Guide: https://www.jotform.com/help/439-Conditionally-Enable-or-Disable-a-Form-Based-on-Time 

Let us know if you have any questions or if you need further assistance. 

Thanks for your reply. I have received an allegation that the JotForm I created expired before the time that I set on the Form. See screen shot below. The last person who accessed the form successfully, did so at 10.24pm AEST. The allegation from another person was that they attempted to register via the JotForm at 11.12pm AEST and it had expired. I suspect that they are lying. Is there any way I can find out if anyone tried to access the form but did not complete it because it had expired? Many thanks

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Please note that submissions are captured only when the form is submitted. Unfortunately it is not possible to see from where user abandoned form or was not able to submit form.

I would suggest you to please take a look at your form's analytics and see if it gives you desired data. The following guide should help you how to check form's analytics: https://www.jotform.com/help/425-Understanding-Form-Analytics-and-Ways-on-How-to-Get-Your-User-s-Info

Hope this helps.

Do get back to us if you have any questions.