Quick answer
Calculate the calendar interval first, then apply the employer's credited-service rules as separate, documented adjustments.
Two numbers, one question
The time between a start date and today is a calendar fact. What counts as service for a particular entitlement is a policy question, and policies exclude things: unpaid leave, career breaks, casual periods before a permanent contract, and sometimes time with a predecessor employer depending on how a transfer was structured.
Calculate the calendar figure first, because it is the baseline every adjustment works from and the only part that is not open to interpretation. Then apply the rules, one visible line at a time.
Use this guide with the right tool: Open the Years of Service Calculator for exact employment service duration between two dates. If the question shifts, compare it with the Employment Duration Calculator or the Career Length Calculator.
Which start date counts
Offer date, contract date, first working day and payroll start can all differ, and after an acquisition or a TUPE transfer there may be an earlier recognised date carried forward from a previous employer.
The recognised service date is what the policy uses, and it is not always the obvious one. Name it in the record along with where it came from, because a figure derived from an undocumented start date cannot be checked.
Completed years, not elapsed portions
Almost every service-based entitlement counts completed years. An employee hired on 12 September has not completed their next service year until 12 September comes round again, however far into the calendar year it is.
This trips people up around annual review cycles, where a leave entitlement or a benefit tier is assumed to apply from the start of a calendar or financial year. The anniversary is what matters unless the policy explicitly says otherwise.
Recording it so it survives
Store the recognised start date and derive the duration, rather than storing a computed figure that goes stale from the moment it is written. Where a snapshot is needed because it fed a decision, store it with its as-at date and treat it as historical.
For anything that might be disputed — redundancy calculation, long-service entitlement, pension accrual — the record should let a reviewer rebuild the figure from the dates without contacting anyone.
Worked example
Substitute your own dates and follow the instructions that actually govern your situation. Where a result sits close to a cutoff, verify the underlying date and rule independently before relying on it.
Common mistakes to avoid
- Using the hire year alone. The start month and day determine every anniversary. A year is not a start date.
- Treating calendar duration as credited service. Policies exclude things. Apply each exclusion as a separate documented step.
- Assuming entitlements start with the calendar year. Almost all service entitlements run from the anniversary unless the policy says otherwise.
Use the right calculator
Each of these runs in the browser, states its assumptions, and links to the neighbouring calculation when the question turns out to be a different one.
Frequently asked questions
Does unpaid leave count as service?
It depends entirely on the policy and jurisdiction. Calculate the calendar figure, then apply the rule and record it.
What about service with a previous employer after a transfer?
Sometimes it carries forward. That is determined by the transfer arrangement and local law, not by arithmetic.
Should I round service up?
Only if the policy says so. Most entitlements count completed years, so a partial year does not qualify.