$dayOfWeek (Get Day of Week)

Last updated: 2026-10-09

$dayOfWeek (Get Day of Week)

$dayOfWeek returns the weekday of a date as an integer: 1 is Sunday, 7 is Saturday — matching JavaScript's Date.getDay(). Often used for weekday-based traffic stats or scheduling. Note numbering starts on Sunday, unlike ISO $isoDayOfWeek (Monday is 1), so confirm the semantics you need. timezone drives the weekday boundary and defaults to UTC.

📝 Syntax

{ $dayOfWeek: { date: <date-expression>, timezone: <timezone> } }

⚙️ Parameters

Returns：Weekday number (1=Sunday, 7=Saturday); null if date is null.

▶ Example

Run the commands below in your local mongosh (requires a running mongod):

// $dayOfWeek: count visits by weekday (Beijing time)
 db.logs.aggregate([
  { $group: {
      _id: { $dayOfWeek: { date: '$ts', timezone: 'Asia/Shanghai' } },
      cnt: { $sum: 1 }
  } }
])

Output：

{ "_id": 1, "cnt": 1240 }
{ "_id": 2, "cnt": 980 }

📌 Notes

• 1 is Sunday, not Monday — a common pitfall; use $isoDayOfWeek for Monday-first
• Combine with $group for weekday-based stats
• Defaults to UTC; pass Asia/Shanghai for China-based business

🏷️ Related Tags

💡 Related Cases

📚 Related Tutorials

❓ FAQ

Web-Tutorial Tech Team

A team of developers maintaining programming tutorials. Each tutorial is written and reviewed by developers with expertise in that field. We work to keep our content accurate and reliable — if you spot an issue, please let us know.

About Us