bash date — format date and timestamp
Quick Answer
# Current date and time (ISO 8601)
date +"%Y-%m-%dT%H:%M:%S"
# 2024-01-15T09:30:00
# Date only
date +"%Y-%m-%d"
# 2024-01-15
# Unix epoch (seconds since 1970-01-01)
date +%sUsage
You need to generate timestamps for log filenames, backups, or script output.
Other causes & fixes
Common format specifiers
%Y four-digit year 2024
%m month (01-12) 01
%d day of month (01-31) 15
%H hour (00-23) 09
%M minute (00-59) 30
%S second (00-59) 00
%Z timezone UTC
%s Unix epoch seconds 1705312200
%N nanoseconds (Linux) 123456789Date arithmetic (GNU date / Linux)
# 7 days ago
date -d "7 days ago" +"%Y-%m-%d"
# Tomorrow
date -d "tomorrow" +"%Y-%m-%d"
# Specific date + offset
date -d "2024-01-01 + 30 days" +"%Y-%m-%d"macOS date arithmetic (BSD date)
# macOS uses -v for arithmetic
date -v-7d +"%Y-%m-%d" # 7 days ago
date -v+1d +"%Y-%m-%d" # tomorrow
# Install GNU coreutils for date -d on macOS
brew install coreutils
gdate -d "7 days ago" +"%Y-%m-%d"Timestamp in a filename
logfile="backup_$(date +"%Y%m%d_%H%M%S").tar.gz"
echo $logfile # backup_20240115_093000.tar.gzRelated