When I use a custom date field as a trigger condition, what do Is within the previous and Is within the next do?
Is within the previous and Is within the next take an integer number of days, which on the back end is translated into multiples of 24 hours.
For example, Custom date field | Is within the next | 3 means the condition will evaluate as true when the timestamp of the custom date field is within the next 72 hours.
The timestamps for date fields are a more complicated issue since they’re not exposed anywhere in the UI or the API. In general, the hidden timestamp related to a custom date field is 12:00 PM on the selected date in the system time of the agent who set the date field.
For more information about creating triggers, see the article: Trigger conditions and actions reference.