How to Convert Timestamp to Date

Quick Answer: Convert Timestamp to Date in Bash

To convert Unix timestamp to date, use date -d @1645382400 to show the date, or date -d @1645382400 +%Y-%m-%d for specific format. To convert date to timestamp, use date -d "2026-02-21" +%s. Both use the date command with different format specifiers.

Quick Comparison: Timestamp Conversion Methods

Operation	Command	Output	Use Case
Epoch to date	date -d @1645382400	Readable date	Log analysis
Date to epoch	date -d "2026-02-21" +%s	Timestamp	Calculations
Custom format	date -d @ts +%Y-%m-%d	Specific format	Reporting
Current time	date +%s	Now timestamp	Scripts

Bottom line: Use date -d @timestamp to read; use date -d "date" +%s to convert to timestamp.

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Convert Unix timestamps (epoch time) to readable date formats and vice versa. Learn converting between timestamps and date strings.

Method 1: Convert Epoch to Date

# Basic conversion
date -d @1645382400

# Output: Sat Feb 21 00:00:00 UTC 2026

# Specific format
date -d @1645382400 +%Y-%m-%d

# Output: 2026-02-21

Format Options for timestamp

timestamp=1645382400

# Date only
date -d @$timestamp +%Y-%m-%d

# Time only
date -d @$timestamp +%H:%M:%S

# Full datetime
date -d @$timestamp '+%Y-%m-%d %H:%M:%S'

# Day of week
date -d @$timestamp +%A

# Custom format
date -d @$timestamp '+%A, %B %d, %Y at %I:%M %p'

Function to Convert Timestamp

#!/bin/bash

epoch_to_date() {
  local timestamp="$1"
  local format="${2:-%Y-%m-%d %H:%M:%S}"

  if [ -z "$timestamp" ]; then
    echo "Usage: epoch_to_date <timestamp> [format]"
    return 1
  fi

  date -d @$timestamp +"$format"
}

# Usage
epoch_to_date 1645382400
epoch_to_date 1645382400 '%Y-%m-%d'
epoch_to_date 1645382400 '%A, %B %d, %Y'

Output:

2026-02-21 00:00:00
2026-02-21
Saturday, February 21, 2026

Convert Date to Epoch

# Convert date string to epoch
date -d "2026-02-21" +%s

# Output: 1645382400

# Convert datetime to epoch
date -d "2026-02-21 14:30:00" +%s

# Output: 1645429800

Function for Date to Epoch

#!/bin/bash

date_to_epoch() {
  local date="$1"

  if [ -z "$date" ]; then
    echo "Usage: date_to_epoch <date>"
    return 1
  fi

  date -d "$date" +%s
}

# Usage
epoch=$(date_to_epoch "2026-02-21")
echo "Epoch: $epoch"

Batch Conversion

#!/bin/bash

# Convert list of timestamps to dates

input_file="$1"

if [ ! -f "$input_file" ]; then
  echo "Usage: $0 <timestamps_file>"
  exit 1
fi

while read timestamp; do
  # Skip empty lines
  [ -z "$timestamp" ] && continue

  # Convert and display
  date_str=$(date -d @$timestamp '+%Y-%m-%d %H:%M:%S')
  echo "$timestamp → $date_str"
done < "$input_file"

Test file (timestamps.txt):

1645382400
1645429800
1645516200

Output:

1645382400 → 2026-02-21 00:00:00
1645429800 → 2026-02-21 14:30:00
1645516200 → 2026-02-22 14:30:00

Practical Example: Log Timestamp Conversion

#!/bin/bash

# File: convert_log_timestamps.sh

log_file="$1"
output_file="${2:-converted.log}"

if [ ! -f "$log_file" ]; then
  echo "Usage: $0 <logfile> [output_file]"
  exit 1
fi

echo "Converting timestamps in $log_file..."

> "$output_file"

while IFS= read -r line; do
  # Check if line starts with timestamp
  if [[ $line =~ ^([0-9]{10})(.*)$ ]]; then
    timestamp="${BASH_REMATCH[1]}"
    rest="${BASH_REMATCH[2]}"

    # Convert timestamp
    readable=$(date -d @$timestamp '+%Y-%m-%d %H:%M:%S')

    echo "$readable$rest" >> "$output_file"
  else
    echo "$line" >> "$output_file"
  fi
done < "$log_file"

echo "✓ Converted log saved to: $output_file"

Format Variations

timestamp=1645382400

# Different formats
echo "ISO 8601: $(date -d @$timestamp --iso-8601=seconds)"
echo "RFC 2822: $(date -d @$timestamp --rfc-2822)"
echo "Compact: $(date -d @$timestamp +%Y%m%d_%H%M%S)"
echo "Time only: $(date -d @$timestamp +%H:%M:%S)"
echo "Day name: $(date -d @$timestamp +%A)"
echo "Unix format: $(date -d @$timestamp)"

Output:

ISO 8601: 2026-02-21T00:00:00+00:00
RFC 2822: Sat, 21 Feb 2026 00:00:00 +0000
Compact: 20260221_000000
Time only: 00:00:00
Day name: Saturday
Unix format: Sat Feb 21 00:00:00 UTC 2026

Round-trip Conversion

#!/bin/bash

# Convert date → epoch → date

original_date="2026-02-21 14:30:00"

# Convert to epoch
epoch=$(date -d "$original_date" +%s)
echo "Original: $original_date"
echo "Epoch: $epoch"

# Convert back to date
back_to_date=$(date -d @$epoch '+%Y-%m-%d %H:%M:%S')
echo "Converted back: $back_to_date"

Output:

Original: 2026-02-21 14:30:00
Epoch: 1645429800
Converted back: 2026-02-21 14:30:00

Timezone Handling

#!/bin/bash

timestamp=1645382400
timezone="${1:-UTC}"

# Convert with specific timezone
TZ=$timezone date -d @$timestamp

# Examples
echo "UTC: $(TZ=UTC date -d @$timestamp '+%Y-%m-%d %H:%M:%S')"
echo "EST: $(TZ=America/New_York date -d @$timestamp '+%Y-%m-%d %H:%M:%S')"
echo "IST: $(TZ=Asia/Kolkata date -d @$timestamp '+%Y-%m-%d %H:%M:%S')"

Practical Example: File Timestamp Interpretation

#!/bin/bash

# Convert file modification time from epoch

file="$1"

if [ ! -f "$file" ]; then
  echo "Usage: $0 <file>"
  exit 1
fi

# Get modification time as epoch
mod_epoch=$(stat -c %Y "$file" 2>/dev/null || stat -f %m "$file" 2>/dev/null)

# Convert to readable format
mod_date=$(date -d @$mod_epoch '+%Y-%m-%d %H:%M:%S')

echo "File: $file"
echo "Modified: $mod_date"
echo "Epoch: $mod_epoch"

Common Formats Table

Format	Example	Code
ISO 8601	2026-02-21T00:00:00+00:00	--iso-8601
RFC 2822	Sat, 21 Feb 2026	--rfc-2822
Human	Saturday, February 21, 2026	+%A, %B %d, %Y
Short	02/21/2026	+%m/%d/%Y
Compact	20260221	+%Y%m%d

Common Mistakes

1. Missing @ symbol - must use @ before epoch: @1645382400
2. Wrong format codes - use lowercase %d for day
3. Timezone not set - epoch is always UTC, use TZ variable to convert
4. Not quoting timestamp - can fail with spaces
5. Using system date instead of -d - need -d flag for conversions

Performance Tips

• Cache conversion results if used repeatedly
• Use awk with strftime for bulk conversions
• Avoid looping date command for large files

Key Points

• Use date -d @$timestamp for epoch conversion
• Use date -d "$date" +%s for date to epoch
• Include @ before timestamp number
• Use + format codes for custom output
• Remember epoch is always UTC

Summary

Converting between timestamps and dates is essential for log analysis and scripting. The date command makes it simple with the @ prefix for epochs and +%s for conversion to epoch.