Quick answer
Record the recognised start date and its source, the reference date, the calendar duration, and any adjustment with its reason. Derive the figure; never store it.
Which start date
There is rarely only one. The offer date, the contract date, the first working day, the payroll start and the recognised service date can all differ, and after a TUPE transfer, an acquisition or a rehire there may be an earlier date that carries forward.
Whichever one the record uses, name it and say where it came from. 'Recognised service date 1 March 2012, carried forward from acquisition, per HR file' is auditable. '2012' is not.
Use this guide with the right tool: Open the Work Anniversary Countdown for the next employment anniversary and completed service duration. If the question shifts, compare it with the Employment Duration Calculator or the Service Milestone Calculator.
Duration is derived, not stored
Tenure changes every day. Any system that stores a computed years-of-service figure is storing something that starts going stale immediately and gives no signal when it does.
Store the start date and derive the duration whenever it is displayed. Where a snapshot genuinely must be kept — because it fed a decision on a particular day — store it with that date and label it as historical.
Adjustments belong on separate lines
Unpaid leave, career breaks, casual periods before permanent employment and other exclusions produce credited service that differs from calendar duration. Folding them into a single number destroys the audit trail.
Record the calendar figure, then each adjustment with its reason and the policy that authorised it, then the resulting credited service. Anyone reviewing can follow the arithmetic and see which step they disagree with, if any.
Anniversaries are a separate calculation
A work anniversary is a calendar anniversary of the recognised start date, found by adding whole years. It is not the same as completed credited service, which may be lower, and the two can drift apart after a break in service.
For recognition programmes this matters: an employee's fifth anniversary and their fifth year of credited service can fall in different years. Decide which the programme is based on and say so, because people notice.
Worked example
Service from 1 March 2012 to 16 August 2026 is 14 years, 5 months and 15 days, or 13 years 11 months credited after excluded leave. Work your own service date through both bases before recording either figure.
A rehire splits the record
The worked example has one start date. A rehire produces a record where the single-figure habit fails outright. Take an employee whose first stint ran from Monday 3 June 2019 to Tuesday 31 May 2022 — 2 years, 11 months and 28 days, or 1,093 days — who was then away for a gap of 1 year, 8 months and 1 day, and whose second stint began on Thursday 1 February 2024. Measured on 16 August 2026, the second stint is 2 years, 6 months and 15 days, or 927 days.
Three totals can now be defended, and the record has to say which one it is reporting. The sum of the two stints is 2,020 days of actual service — expressed as a single span from the first start date, 5 years, 6 months and 10 days. The span from the first start date to the reference date is 7 years, 2 months and 13 days, or 2,631 days. The two figures reconcile exactly: 2,020 days of service plus 611 days of gap equals the 2,631-day span. If a record's service figure and its span do not reconcile through the gap like this, one of the three numbers is wrong, and the record gives no way to tell which.
Written in the format this guide recommends, the entry carries both stints as separate lines, each with its own start and end dates and sources, the gap as its own line rather than an adjustment folded into a total, and the credited figure labelled as the sum of stints under whatever policy governs rehires. A reviewer can then follow every step. What they cannot do is rescue a record that stored only "seven years" — a figure that matches the span, contradicts the service, and conceals the break that explains both.
The anniversary drift from the worked example grows sharper over time. The employee who started on 1 March 2012 reaches their fifteenth work anniversary on Monday 1 March 2027, when their calendar service is exactly 15 years and their credited service, after the six months of excluded leave, is 14 years and 6 months. Fifteen years of credited service is not reached until Wednesday 1 September 2027 — six months after the anniversary. A recognition programme keyed to anniversaries celebrates in March; one keyed to credited service celebrates in September. Both dates are correct, they are half a year apart, and only the record can say which event the programme is actually marking.
A rehire also forces the anniversary question the worked example only implies: anniversary of which start? Counted from the original start, this employee's seventh anniversary fell on Wednesday 3 June 2026. Counted from the rehire, their second anniversary fell on Sunday 1 February 2026 — a date no workplace will celebrate, being a Sunday, which is its own small argument for writing the basis down. The two anniversaries are both real, they are four months apart, and a recognition programme that never chose between them will eventually honour the wrong one in front of the employee, who will know. The record that lists both start dates, each with its source, makes the choice visible and therefore arguable in advance — which is the whole purpose of keeping it.
Common mistakes to avoid
- Recording only a year. Start month and day determine every anniversary and every duration. A year alone is not a start date.
- Storing a computed tenure figure. Store the date and derive the duration, or the record decays silently.
- Merging adjustments into one number. Keep each adjustment on its own line with its reason, or the figure cannot be audited.
Use the right calculator
Use Work Anniversary Countdown for the next anniversary and completed service, the Employment Duration Calculator for calendar duration of service, and the Service Milestone Calculator for a future service milestone.
Frequently asked questions
Which start date should the record use?
The recognised service date under your policy, with its source named. Where several dates exist, record them all.
Do anniversaries and credited service always match?
No. After a break in service they can differ by months or years. Say which one a programme uses.
What is the minimum to record?
Recognised start date and source, reference date, calendar duration, each adjustment with its reason, and the resulting credited service.