Bash Script to Convert Date to Unix Timestamp

Use the Bash command date -d "your_date" +%s to convert a date string to a Unix timestamp, for example: date -d "2024-06-01 12:00:00" +%s.

Examples

Input2024-06-01 12:00:00

Output1717204800

Input1970-01-01 00:00:00

Output0

Input2024-12-31 23:59:59

Output1735689599

How to Think About It

To convert a date to a Unix timestamp in Bash, you use the date command with the -d option to specify the date string, and the format +%s to output the time as seconds since January 1, 1970 (Unix epoch). This converts human-readable dates into a numeric timestamp.

Algorithm

1

Get the date string input from the user or script argument.

2

Use the <code>date</code> command with <code>-d</code> to parse the date string.

3

Format the output with <code>+%s</code> to get the Unix timestamp.

4

Print the resulting timestamp.

Code

bash

#!/bin/bash

# Read date string from argument
input_date="$1"

# Convert to Unix timestamp
timestamp=$(date -d "$input_date" +%s)

# Print the timestamp
echo "$timestamp"

Output

1717204800

Dry Run

Let's trace the input '2024-06-01 12:00:00' through the script

1

Receive input date string

input_date = '2024-06-01 12:00:00'

2

Run date command to convert

date -d '2024-06-01 12:00:00' +%s

3

Get Unix timestamp output

1717204800

4

Print the timestamp

echo 1717204800

Step	Action	Value
1	Input date string	2024-06-01 12:00:00
2	Convert with date command	1717204800
3	Output timestamp	1717204800

Why This Works

Step 1: Using date command with -d

The -d option tells date to parse the given date string instead of the current date.

Step 2: Formatting output as Unix timestamp

The +%s format outputs the time as seconds since the Unix epoch (January 1, 1970).

Step 3: Printing the result

The script stores the timestamp in a variable and prints it, making it easy to use in other scripts or commands.

Alternative Approaches

Using date with UTC timezone

bash

#!/bin/bash
input_date="$1"
timestamp=$(date -u -d "$input_date" +%s)
echo "$timestamp"

This method converts the date assuming UTC timezone, useful if you want consistent timestamps regardless of local timezone.

Using Python from Bash

bash

#!/bin/bash
input_date="$1"
timestamp=$(python3 -c "import time; import sys; print(int(time.mktime(time.strptime(sys.argv[1], '%Y-%m-%d %H:%M:%S'))))" "$input_date")
echo "$timestamp"

This uses Python to convert the date, helpful if <code>date -d</code> is not available or for more complex date formats.

Complexity: O(1) time, O(1) space

Time Complexity

The conversion uses a single system call to date, which runs in constant time regardless of input size.

Space Complexity

Only a few variables are used to store input and output, so space usage is constant.

Which Approach is Fastest?

Using the built-in date command is fastest and simplest; calling Python adds overhead but offers more flexibility.

Approach	Time	Space	Best For
date -d +%s	O(1)	O(1)	Simple date strings, fast conversion
date -u -d +%s	O(1)	O(1)	UTC timestamps, timezone consistency
Python time.mktime	O(1)	O(1)	Complex formats, portability when date command is limited