After editing a file geodatabase feature class, the time stamp in the date modified column of the ArcCatalog contents window does not match the time when the editing was done. This is because ArcGIS software does not handle the update of time due to performance constraints. Instead, the operating system is used for identifying the time when the feature class was last modified.
This time does not get updated until the ArcMap application is closed because of the lock files that are present in the file geodatabase folder. When ArcMap is closed, the lock is released which is considered as a 'change' to the feature class by the operating system and this is the time shown is ArcCatalog.