Nth month dimension
Nth month is the dimension that numbers months by their offset from the start of the selected range — month 0, month 1, and so on. It is the longest-horizon member of the nth-period family, built for lifecycle and long-term cohort analysis where retention is measured over many months. Its numbering is relative to the report range, and like its siblings it carries no fixed calendar meaning.
What this means
Nth month indexes months from the start of the chosen range, letting cohorts that began in different calendar months be compared on the same month-0, month-1 axis. It is the right grain for slow lifecycle effects that take months to surface.
It extends the nth-day and nth-week pattern to the longest practical horizon.
Horizon and retention limits
Long nth-month analysis depends on retaining enough historical data; GA4's event-data retention setting can truncate the deepest months in exploration-level views. Combined with months of unequal length, this means later month buckets can look thinner for structural reasons.
Verify retention and account for partial trailing months before reading a decline as real churn.
- Offset in months from the range start
- Longest-horizon nth-period dimension
- Depth bounded by data-retention settings
How it appears in analytics and logs
An nth month value is a relative month offset, not a calendar month. It is interpretable only within the range that generated it.
Diagnostic use case
Use nth month to align long-horizon cohorts on their month-one, month-two and later behaviour for lifecycle and retention analysis.
What WebmasterID can help detect
WebmasterID can express timing as months-since-baseline first-party, supporting lifecycle analysis without third-party tracking.
Common mistakes
- Reading retention-truncated late months as churn.
- Treating nth month as a calendar month.
- Ignoring unequal month lengths in the curve.
Privacy and accuracy notes
Nth month records a relative month index, not identity. WebmasterID can index months from a baseline first-party without profiling visitors.
Related pages
- Nth week dimension
Nth week is the dimension that numbers weeks by their offset from the start of the selected range — week 0, week 1, and so on. It is the weekly analog of nth day, built for multi-week retention curves and cohort decay where you want week-1 retention to align across cohorts regardless of when each began. Its numbering is relative to the report's range and resets when the range changes.
- Month dimension
Month is the dimension that groups events by calendar month (01–12) in the property time zone. It is the coarse grain for seasonal and budget-cycle reporting. Its main pitfall is that months have different lengths, so raw month-over-month comparisons mix a 28-day February with a 31-day March, which can masquerade as a trend if you do not normalise per day.
- Cohort dimension
The cohort dimension groups users by a shared starting point — typically their acquisition date — so you can follow each group's behaviour across subsequent days, weeks, or months. GA4 builds cohorts in the Cohort exploration from a first-touch criterion and a return criterion. It is the backbone of retention analysis, but small cohorts and identity loss can make later-period values unstable, so trends matter more than single cells.
- Web analytics
Long-horizon lifecycle analysis first-party.
Sources and verification notes
- Google Analytics Help — [GA4] Dimensions, metrics, and other termsDefines nth-month as an offset from the range start.
- Google Analytics Help — [GA4] Data-retention settingsBounds how deep long-horizon cohort analysis can reach.
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.