Hi! Does the formula field support finding the mid point between two dates?
Example:
I have an intern that starts on May 11th, 2026 and the internship ends on August 14th, 2026. Halfway through the two dates, I want to automate an email to the intern asking him to fill out a form. Can the formula field calculate that midpoint date?
2026-04-20 Edit:
User can create a rule that triggers off the second custom date field but it will only run once (usually after midnight)
Yes the formula field can calculate that midpoint by using the advanced editor, then “(End Date - Today) / 2” but unfortunately it will only show that amount as a duration, not a date and also, rules cannot yet be triggered based on sums of a formula, only when a formula field is changed.
So I believe the only way of doing this is either manually, having a hire date field, a midpoint date field, and a last day field, using something like Zapier to bring in that mid point date automatically, or possibly using AI teammates to prompt and monitor something like that but I’ve never tested it before.
Thank you for the input! I tried the formula given and that does tell me how many weeks but like you mentioned it would not show me a date. It would be neat to see this as a future feature. Now, go get some coffee ha!
Hi @AbigailB , I thought this should be possible so I gave it a whirl.
Here is the end formula:
You can try to copy/paste this into the Advanced editor:
[[$DATESUBTRACT_FUNCTION]]([[$DUE_DATE]], (([[$DUE_DATE]] - [[$STARTED_AT]]) / 2))
If you get an error, you may need to build this and two steps to ‘fool’ Asana.
First create this formula and save it:
Here it is in action:
However, as @neonrain.club correctly mentioned, a rule cannot be triggered by a formula field as it is not treated the same as other (true) Date type fields which include triggers such as ‘When {date field} is approaching / overdue’.
However, I tried creating a Date field called ‘Midpoint date’ and created the following rule to populate/map over the formula’s date value into this date field so that rules could be used when date is approaching/overdue.
The rule works but only when triggered manually - unfortunately, even though the trigger is when the formula ‘Midpoint’ value is changed, it doesn’t trigger when I change the Start & Due dates. I believe this is related to an ongoing bug that I’ve raised here:
Hi, @AbigailB and @Richard_Sather
I came up with a way to set ‘midpoint date’ automatically.
Look at the following rule;
Technically it could fail because the setting action could be done before calculating ‘midpoint’. But it didn’t fail whenever I tested.
Nice, @Tetsuo_Kawakami 
@Richard_Sather and @Tetsuo_Kawakami thank you for the help! I was able to get the formula working based on the guidance you both provided. Basically, one custom field with the formula, and a custom field date field to pull the value.
I think I am running into the issue Richard mentioned that the rules do not seem to trigger properly. After sorting the date issues, I turned around and made a second rule for an external email action and so far I have not been able to make it work.
Hi @AbigailB , glad to hear it!
For triggers for date approaching, you will need to wait until a bit after midnight for these rules to fire on tasks that their due date is on that day after midnight, in your local time zone.
Ah!! I keep forgetting about the midnight sync for those types of rules!! Appreciate the help.
Asana pushed a recent update where such formula fields will now trigger rules, like the original version I posted above. 
