Summary: The date type for crash reports was updated in D29327501 (aff02b2ca1) from `Date` to `number`. Unset values were previously `null` but became `NaN` in this change. `NaN` is nonnull so the backup value of `Date.now()` was not getting triggered properly and leading to "Invalid Date" to show up in the UI.
Reviewed By: passy
Differential Revision: D31702757
fbshipit-source-id: da93b1f79eb633b2f49dcffbe680d56d47a23ea0
9d34c90b9a