Time Difference Calculator

TL;DR

Compute the difference between two times (start/end). Use it for shifts, client work sessions, meetings, and quick billing math.

Who this is for

• Anyone calculating “how long was this session?”
• Contractors who want a quick duration before logging it in a timesheet.
• Employees who need to sanity-check a shift plan (start/end) without a spreadsheet.

How to use it

1. Enter start and end time.
2. Read the computed duration (hours + minutes).
3. If you invoice, apply your rounding rule (if any) before copying totals into an invoice.

Tip: keep a consistent time format

Use a consistent format across your logs (e.g., 09:05 not 9:5). Small formatting differences create mistakes when you copy/paste into spreadsheets or client portals.

Common workflows

One-off sessions (contracting)

You worked from 09:30 to 11:10 on a client request. Compute duration, then log it with a short note in Attendance sheet.

Split days

If you have multiple sessions in a day (e.g., morning + afternoon), calculate each session separately, then add totals using Hours total.

Proof for disputes

If a client asks “when did you work on this?”, a simple start/end record with notes is often enough to clarify.

Worked examples

Example 1: short session

09:30 → 11:10.

Example 2: longer block

13:05 → 17:40.

Example 3: billing check with rounding

Compute duration, then round using your contract’s rule (e.g., to 15-minute increments) and keep it consistent across the month.

Example 4: shift duration (quick check)

If your shift is 08:00 → 16:30, compute the raw duration first. If you need to subtract breaks, switch to Hours with break.

Gotchas (important)

Crossing midnight

If end is “before” start, you likely crossed midnight. Split it:

• 22:00 → 24:00
• 00:00 → 02:00 Then add the two durations.

Breaks are not included here

If you need to subtract a break, use Hours with break.

Time zone and DST

This is time arithmetic, not calendar/timezone logic. Treat the times as in the same timezone unless your contract explicitly specifies otherwise.

Rounding for billing (avoid surprises)

If you bill by the hour, pick a rounding rule and apply it consistently:

• Round to 15 minutes (0.25h) for simple invoicing.
• Round to 6 minutes (0.1h) if you want more granular billing.

Decide whether you round per session or per day. Rounding per day often feels fairer to clients because small sessions don’t get rounded up multiple times.

FAQ

Should I log every tiny session?

If you bill hourly, yes — tiny sessions add up and create a clearer audit trail. If you bill daily/monthly, you can log more coarsely (but keep notes).

What if my client works in a different timezone?

Agree on one timezone for reporting (yours, theirs, or UTC) and stick to it in every report. This tool assumes both times are in the same timezone.

What next?

Use Attendance sheet for monthly tracking and CSV exports.

Related tools

What you’ll get (outputs)

• Total duration in hours + minutes (human-friendly).
• A clean number you can copy into a log (and optionally convert to decimal hours if your billing uses it).
• A repeatable workflow for “start/end” time entries so your monthly totals stay consistent.

Common mistakes (and how to avoid them)

• Mixing formats (9:5 vs 09:05): stick to HH:MM to avoid copy/paste errors.
• Rounding differently each day: pick one rule and apply it consistently (per day is usually fairer than per session).
• Forgetting breaks: if breaks are not billable calculate net time in Hours with break before rounding.
• Crossing midnight: treat it as two segments (before and after midnight), then add.
• Timezone drift: when working with international clients, agree on one timezone for reporting (or UTC) and stick to it.

Copy/paste formats (useful for invoices and audits)

Simple line (client-friendly)

2025-12-28 — 09:30–11:10 — 1h 40m — Bugfix & deployment support

Daily summary (good for “per-day rounding”)

2025-12-28 — total 6h 15m (rounded to 6h 15m) — 3 sessions — Notes in tracker

If your client requires decimal hours

If your agreement uses decimal hours, convert only after you’ve decided whether you round per session or per day:

• 1h 30m → 1.5h
• 1h 45m → 1.75h

When to use IT Jobs List tools together

• Start end → From–to time
• Breaks → Hours with break
• Totals and conversions → Hours total
• Monthly export and client-facing reporting → Attendance sheet

Related guides

• Timesheet best practices

Next steps (IT Jobs List)

For timeAttendance sheets, consistency beats “granularity”: same rounding rule and the same style of context notes.

Related tools

Related guides

• Timesheet best practices for IT contractors

Quick recommendation

• Save your assumptions (rates, breaks, thresholds) so you can reproduce the result.
• If you use the output in an invoice/offer, include a short explanation (what’s included and what’s not).

Practical checklist (IT Jobs List)

• Decide: rounding per session or per day (and write the rule down).
• Track breaks separately if they’re not billable.
• At month end, export and keep an audit trail.