| Metric | Value | Copy |
|---|---|---|
| {{ row.label }} | {{ row.value }} |
| Checkpoint | Timestamp | Offset | Copy |
|---|---|---|---|
| {{ milestone.label }} | {{ milestone.timestamp }} | {{ milestone.offset }} |
Time intervals are the gaps between two moments on the calendar and clock, expressing how long passes from one reference point to another. A time difference calculator between two dates and times helps turn those scattered timestamps into a single clear picture you can discuss and share. Understanding that span is useful when you plan projects, track deadlines, or simply want to know how long something really took.
You provide a start moment and an end moment, each with a date and an optional clock time. The calculator turns them into totals in years, months, weeks, days, hours, minutes, and seconds, plus a short readable summary. It also highlights the midpoint between them and shows how many of those days fall inside your chosen working week so you can compare calendar time with business time.
Many real timelines involve travel or teams spread across regions, so the calculator lets you choose whether each moment is interpreted in local time, in a universal reference time, or with a fixed offset. This keeps you from counting daylight saving jumps twice and makes cross region comparisons more trustworthy. It also exposes checkpoints at quarter and halfway marks, which are handy when scheduling progress reviews or phased rollouts.
Results are calculated from civil time rules on your device and work best when your inputs use consistent clocks and offsets. They do not replace legal records, payroll systems, or ticketing logs, so always confirm critical decisions against your official sources. Repeating the same comparison with slightly adjusted dates can also reveal how sensitive your plans are to small shifts.
When you return to the same pair of moments later, focus on changes in working day counts and in the milestone schedule rather than the raw totals alone. That pattern will tell you whether your timeline is stretching, compressing, or simply moving as expected.
Date–time inputs are represented as a calendar date combined with a clock time, yielding two named instants t_start and t_end on a civil timeline. Each instant is interpreted either in the device’s local zone, in Coordinated Universal Time (UTC), or as a fixed offset from UTC in 15‑minute steps between UTC−12:00 and UTC+14:00.
The core quantity is the elapsed duration between the two instants. Internally the engine computes the signed difference in milliseconds, then takes the absolute value for reporting so the breakdown is always non‑negative even when the end precedes the start.
| Symbol | Meaning | Unit/Datatype | Source |
|---|---|---|---|
| Δt | Absolute duration between end and start instants | millisecond | Derived |
| t_start | Start timestamp instant | Date–time | Input |
| t_end | End timestamp instant | Date–time | Input |
| Y_total | Total span in years (decimal) | year | Derived |
| M_total | Total span in months (decimal) | month | Derived |
| W_total | Total span in weeks (decimal) | week | Derived |
| D_total | Total span in days (decimal) | day | Derived |
| H_total | Total span in hours (decimal) | hour | Derived |
| Min_total | Total span in minutes (decimal) | minute | Derived |
| S_total | Total span in seconds (decimal) | second | Derived |
| W_work | Count of working days inside the span | day | Derived |
| W_non | Count of non‑working days inside the span | day | Derived |
Consider a start timestamp of 2024‑03‑04 00:00 in local time and an end timestamp of 2024‑03‑08 00:00 with the same mode and a Monday–Friday working week. The earlier instant is the start, so the signed difference is four whole days.
The working‑day counter steps across four midnights from Monday through Thursday, classifying each as a working day and returning 4 working days and 0 non‑working days, matching the table and chart outputs.
For the calendar breakdown the engine walks from the earlier instant to the later one in stages: years, then months, then days, and finally hours, minutes, seconds, and remaining milliseconds. This honours month lengths and leap‑year rules instead of assuming fixed numbers of days per month or year.
Decimal totals are computed directly from the difference in each unit using the underlying date engine and then formatted to the number of decimal places selected in the advanced controls. The integer summary badges for days, hours, minutes, and seconds apply a floor so they always show whole numbers that never exceed the corresponding decimal totals.
Milestone checkpoints are produced by multiplying the absolute duration in milliseconds by fixed ratios of 0, 0.25, 0.5, 0.75, and 1. Each result is added to the earliest instant to form the Timeline Milestones table, while the Midpoint badge reuses the halfway value in a compact display format.
| Parameter | Meaning | Unit/Datatype | Typical Range | Sensitivity | Notes |
|---|---|---|---|---|---|
| Start timestamp | First reference date and optional time | Date + time | Any valid civil date | High | Anchors chronology and all totals |
| End timestamp | Second reference date and optional time | Date + time | Any valid civil date | High | Defines the span relative to the start |
| Start timezone mode | How the start instant is interpreted | local | UTC | offset | Local by default | High | Choose offset or UTC for cross‑region data |
| End timezone mode | How the end instant is interpreted | local | UTC | offset | Local by default | High | Can differ from the start when needed |
| Custom UTC offset | Fixed offset when mode is set to offset | Integer minutes | −720 to +840 | Medium | Available in 15‑minute steps across the range |
| Working week | Which weekdays count as working days | Enum | Mon–Fri, Mon–Sat, Sun–Thu | Medium | Changes the split between working and non‑working days |
| Decimal places | Max decimal digits in unit totals | Integer | 0 to 9 | Low–Medium | Affects readability, not internal precision |
| Field | Type | Min | Max | Step/Pattern | Error Text | Placeholder |
|---|---|---|---|---|---|---|
| Start date | Date input | Browser default | Browser default | Calendar date only | Enter valid start and end dates. | None |
| Start time | Time input | 00:00 | 23:59 | HH:MM, seconds default to 00 | Enter valid start and end dates. | None |
| End date | Date input | Browser default | Browser default | Calendar date only | Enter valid start and end dates. | None |
| End time | Time input | 00:00 | 23:59 | HH:MM, seconds default to 00 | Enter valid start and end dates. | None |
| Decimal places | Range slider | 0 | 9 | Step 1 | Constrained by slider position | N/A |
| UTC offset | Select input | −720 minutes | 840 minutes | 15‑minute increments | Constrained by options list | N/A |
| Input | Accepted Families | Output | Encoding/Precision | Rounding |
|---|---|---|---|---|
| Start and end timestamps | HTML date and time fields (YYYY‑MM‑DD, HH:MM 24‑hour) | Readable summary and breakdown rows | Text formatted as YYYY‑MM‑DD HH:mm or HH:mm:ss | Locale rounding to 0–9 decimal places |
| Timezone modes and offsets | Local, UTC, or custom UTC±HH:MM offsets | Adjusted instants for all calculations | Offsets stored as integer minutes | No rounding, exact minute offsets |
| Working week selector | Mon–Fri, Mon–Sat, or Sun–Thu calendars | Working and non‑working day counts | Whole‑day counts only | No rounding, pure integer counts |
| Export and copy actions | CSV, DOCX, JSON, PNG, JPEG, WebP | Files or clipboard text for reuse | Matches on‑screen numeric formatting | Uses already‑rounded values from the UI |
The calculations follow common civil timekeeping conventions, including calendar month and year lengths, leap‑year behaviour, and familiar business‑week patterns. For regulated domains or scientific timing, defer to the specific standards and documentation required by your organisation when interpreting or archiving results.
All calculations run in the browser using the values you enter, and exports such as CSV, DOCX, JSON, or chart images are generated locally without sending data to remote servers. Treat the outputs as planning aids rather than definitive legal, payroll, or compliance records, and handle any saved files under your usual security and retention policies.
Calculating the gap between two timestamps follows a short sequence from choosing inputs to reading the resulting breakdown and checkpoints.
For example, set the start to the morning your project begins and the end to a planned delivery date to see both total elapsed time and expected working days.
Pro tip: tap Swap start & end to flip the direction of a comparison while keeping the same two instants, which can surface asymmetries in how teams talk about that timeline.
No schedule or timestamp values are sent to remote services by this calculator. Dates, times, and derived outputs live only in the page session, and files such as CSV, DOCX, JSON, or chart images are generated in the browser for you to save or discard.
Clear downloaded files if they contain sensitive plans or personal schedules.The core difference is computed in milliseconds using the runtime’s date and time engine. Calendar breakdowns respect month lengths and leap years, while decimal totals are rounded to the number of digits you select. Working‑day counts use whole local days between midnight boundaries, so they are always integer values.
If precision beyond milliseconds is required, rely on domain‑specific tooling.Inputs use standard browser date and time fields. Dates follow a year‑month‑day structure such as 2024‑03‑04, and times use a 24‑hour clock with hours and minutes like 09:30. Seconds are optional and default to 00 when omitted. Invalid combinations simply trigger the generic request to enter valid start and end dates.
Exact formatting may vary slightly with your locale settings.Once the page and its scripts are loaded, all calculations continue to run in the browser without requiring a network connection. Clipboard operations and file downloads are local actions, although some managed environments may still restrict saving files or copying to the system clipboard.
Reloading the page while offline may fail if assets are not cached.The calculator does not ask for a sign in, email address, or other identity information. Any pricing, rate limits, or reuse conditions come from the site that hosts the tool, so consult that site’s terms if you plan to embed outputs in internal or commercial workflows.
Check your organisation’s policies before sharing exported schedules externally.To compare events in different places, set each timestamp using the timezone mode that matches where it was recorded. For example, treat departure and arrival as fixed offsets, or use UTC for both when coordinating across teams. The working‑day calendar always follows the local interpretation chosen on your device.
When in doubt, align both sides to UTC for neutral comparisons.Borderline cases occur when your span touches the edge of a day or sits near a daylight saving change. The calculator uses whole days for working‑day counts and rounds decimal totals to your chosen precision, so if a decision depends on that boundary you should also test slightly earlier and later timestamps.
Use multiple nearby runs to understand the sensitivity of edge decisions.Use the buttons in each tab to copy CSV to the clipboard, download CSV files, export a Word document summary, grab chart images, or save a JSON payload. Every export mirrors the values shown on screen, so you can paste them into reports, tickets, or other tools without retyping.
If downloads fail, check browser permissions or try another browser.Most issues come from invalid dates, unexpected timezone choices, or blocked clipboard and download permissions. Use the checks below to quickly restore a trustworthy duration readout.
If the reported duration is clearly impossible for your scenario, for example centuries between nearby dates, stop and verify your device clock, timezone, and locale settings before trusting any exported tables or charts.