my-docs/Linux/Basic Administration/31-date.md

Essential Date and Time Manipulation Commands

This document outlines common shell commands used for working with dates and times, essential for scripting, logging, and system administration tasks.

1. Creating Epoch Timestamps

The date command is versatile for generating timestamps in various formats, most notably the Unix epoch time (seconds since 1970-01-01 00:00:00 UTC).

Command to Create Epoch Time (Milliseconds Precision)

This command converts a specific human-readable date and time into the epoch time, including milliseconds (%3N).

date -d "2026-01-13 14:31:26" +%s%3N

2. Formatting Current Date and Time

Displaying the current date and time in a readable or specific format.

Command	Description	Example Output (Varies)
date	Default display	Wed Jan 17 10:30:00 UTC 2026
date +'%Y-%m-%d %H:%M:%S'	Standard ISO format	2026-01-17 10:30:00
date +%s	Current epoch time (seconds)	1737154200

3. Converting Epoch to Human Readable

Converting a numeric epoch timestamp back into a readable format.

# Assuming $EPOCH_TIME holds a value like 1737154200
date -d @"$EPOCH_TIME"

4. Date Arithmetic

Calculating dates relative to the current time.

Command	Description	Example Output (Varies)
date -d "yesterday"	The previous day	Tue Jan 16 ...
date -d "2 weeks ago"	Two weeks prior	Thu Jan 03 ...
date -d "+1 hour"	One hour from now	Wed Jan 17 11:30:00 UTC 2026