Day of week dimension
Day of week is the dimension that groups events by weekday (Sunday through Saturday, or a 0-6 index) so you can see weekly patterns. It is derived from each event's timestamp interpreted in the property's reporting time zone. The big caveat: weekday boundaries depend on that time zone, so a global audience spanning many zones will have its 'days' defined by your reporting clock, not theirs.
What this means
Every event has a timestamp. The day of week dimension converts that timestamp into a weekday label — GA4 exposes both a numeric dayOfWeek (0-6) and a name. Grouping by it reveals weekly cadence: which days draw traffic, when conversions cluster, when to publish or send.
It is one of several time dimensions (alongside hour, date, week) derived from the same timestamp.
Time zone is the catch
The weekday is assigned using the property's reporting time zone. Change that time zone and events near midnight can shift to the adjacent day, subtly altering weekday charts. The change is not retroactive in GA4, so historical and new data can be bucketed on different clocks.
For a worldwide audience, your reporting day is a single global cut: a visitor's Saturday evening in one region may fall on your Sunday. Read weekday patterns as 'in our reporting zone', not as each visitor's local week.
- Derived from the event timestamp (0-6 index or name)
- Weekday assigned in the property's reporting time zone
- Time-zone changes are not retroactive in GA4
How it appears in analytics and logs
A day of week value buckets an event by weekday in the property time zone. Apparent weekday patterns can shift if you change the reporting time zone, and a global audience's local weekends may straddle two reported days.
Diagnostic use case
Use day of week to find weekly rhythms and schedule around them, while remembering the weekday is assigned in your reporting time zone, not each visitor's local one.
What WebmasterID can help detect
WebmasterID derives weekday from first-party event timestamps, so weekly patterns are available without profiling visitors or using third-party data.
Common mistakes
- Forgetting weekday is bucketed in your reporting time zone.
- Assuming a time-zone change retroactively re-buckets history.
- Reading a global audience's weekdays as their local days.
Privacy and accuracy notes
Day of week is derived from a timestamp, not from identity. WebmasterID computes it first-party without any personal data.
Related pages
- Hour of day dimension: intraday timing patterns
Hour of day is the dimension that buckets events into one of 24 hours (00-23) so you can read intraday rhythms — when traffic peaks, when conversions happen. Like day of week, it is computed from the event timestamp in the property's reporting time zone. Daylight-saving transitions and a globally distributed audience both complicate it: the hour is your clock's hour, not the visitor's.
- Country dimension (coarse, edge-derived)
The country dimension assigns each visit a country, derived by looking up the visitor's IP address in a geolocation database — often at the CDN edge. It is intentionally coarse: country-level, not address-level. VPNs, proxies, mobile carrier routing, and corporate egress can all place a visit in the wrong country, so it is a strong aggregate signal and a weak per-visit one.
- Session ID dimension: scoping events to one visit
Session ID is the dimension that ties a burst of events together into one session. In GA4 it is derived from the ga_session_id parameter set when a session_start event fires, and it pairs with the client or user ID to be unique. A session ends after a timeout of inactivity (30 minutes by default), so the same person returning later gets a new session ID — which is why session counts respond to the timeout setting.
- Web analytics
Find weekly patterns from first-party timestamps.
Sources and verification notes
- Google Analytics Help — [GA4] Dimensions and metrics (dayOfWeek)Defines dayOfWeek and its time-zone-based derivation.
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.