$dateDiff
Reference group: Date expressions
What it does
Counts unit boundaries crossed, not simply elapsed milliseconds divided by a constant.
Syntax
{$dateDiff: { startDate, endDate, unit, timezone?, startOfWeek? }}
Use case
Calendar duration calculations.
$dateDiff: practical example
{ $project: { daysOpen: { $dateDiff: { startDate: "$openedAt", endDate: "$$NOW", unit: "day" } } } }💡 Explanation
Counts unit boundaries crossed, not simply elapsed milliseconds divided by a constant.
When to use it
Calendar duration calculations.
Key Takeaways
- Counts unit boundaries crossed, not simply elapsed milliseconds divided by a constant.
- Typical use: Calendar duration calculations.