A tick is 100 nanoseconds, or one ten-millionth of a second. A .NET DateTime stores the number of ticks elapsed since midnight on 1 January in the year 1, in the proleptic Gregorian calendar.

How do ticks relate to Unix time?

The Unix epoch of 1 January 1970 corresponds to 621,355,968,000,000,000 ticks. The tool subtracts that offset to map a tick count onto a normal date and adds it back when converting the other way.

Why does the tool use BigInt?

Tick counts can exceed the safe integer range of a JavaScript number. Using BigInt keeps the arithmetic exact across the whole 64-bit range, so no precision is lost in the high-order digits.

Can it show fractions of a second?

Yes. If the tick count has a sub-second component, the result shows the full seven-digit 100-nanosecond fraction rather than rounding to milliseconds.

What is the maximum tick value?

DateTime.MaxValue is the last tick of 31 December 9999, which is 3,155,378,975,999,999,999 ticks. The tool rejects values above this as out of range.

.NET DateTime Ticks Converter

What .NET ticks are

In .NET a DateTime is stored as a single number called ticks. One tick is 100 nanoseconds, and the count starts at midnight on 1 January of the year 1. That fine resolution and distant origin make raw tick values hard to read, so this tool converts them to ordinary UTC dates and back, keeping full precision the whole way.

How it works

The key constant is the tick value of the Unix epoch. Midnight on 1 January 1970 is 621,355,968,000,000,000 ticks. To turn a tick count into a date the tool subtracts that offset, divides by 10,000 to reach milliseconds for a standard date object, and then re-attaches the leftover 100-nanosecond fraction so nothing is lost. The reverse direction multiplies the date’s milliseconds by 10,000 and adds the epoch offset back.

All of this is done with BigInt, because a 64-bit tick count is far larger than the range a JavaScript number can hold exactly.

638000000000000000  ->  2022-09-28T22:13:20Z
2022-09-12T07:46:40Z ->  637985656000000000

Example and notes

Tick values you encounter in logs and serialized objects are almost always in UTC, which is how this tool interprets and emits them. If you have a local time instead, convert it to UTC before entering it, otherwise the result will be off by your timezone offset. The maximum supported value is the final tick of the year 9999, matching DateTime.MaxValue; larger inputs are rejected as out of range.