truncateNanoseconds

Signature

truncateNanoseconds(nanoseconds: bigint, unit: NanosecondTruncationUnit): bigint

Truncate nanoseconds since the Unix epoch to the precision a store can actually hold.

• Floors toward negative infinity, so pre-1970 values truncate the same way post-1970 ones do: truncateNanoseconds(-1500n, "us") is -2000n, not -1000n. Rounding toward zero would make the result jump direction either side of the epoch.
• Call this before writing to a store that cannot hold nanoseconds — PostgreSQL timestamptz and MySQL DATETIME(6) hold microseconds, Date-based APIs hold milliseconds — so the value read back equals the value written.
• Idempotent: truncating an already-truncated value returns it unchanged.
• Returns 0n on invalid input, including nanoseconds outside the range Temporal.Instant can represent. 0n is also the epoch itself — validate first when the two must be told apart.

Parameters

Parameter	Type	Description
nanoseconds	bigint	nanoseconds since the Unix epoch (bigint)
unit	NanosecondTruncationUnit	target storage precision, “ms” (milliseconds) or “us” (microseconds)

Returns

truncated nanoseconds as a bigint, or 0n on invalid input

Types

NanosecondTruncationUnit

Storage precision a nanosecond value can be truncated to.

import type { NanosecondTruncationUnit } from "@northguild/gmt";

"ms" | "us"

Examples

import { truncateNanoseconds } from "@northguild/gmt/precision/calculate";

truncateNanoseconds(1710072000123456789n, "us") // 1710072000123456000n

nanoseconds

output

 

Source

precision/calculate/truncateNanoseconds.ts