To get the current date in YYYY-MM-DD format in a shell script, use date +%Y-%m-%d. This works on Linux (GNU coreutils) and macOS (BSD) and produces output like 2026-06-18. The format string %Y gives the four-digit year, %m the zero-padded month, and %d the zero-padded day.

Basic Usage

Assign the formatted date to a variable and use it in your script:

1#!/bin/bash
2
3today=$(date +%Y-%m-%d)
4echo "Today is $today"

Output:

Today is 2026-06-18

The $(...) syntax runs the date command in a subshell and captures its output. No quotes are needed around the format string as long as it contains no spaces, but quoting is a good defensive habit:

today=$(date "+%Y-%m-%d")

Common Date Format Variations

The date command supports many format specifiers. Here are the most useful combinations:

Date Arithmetic

GNU date (Linux)

GNU date supports the -d (or --date) option for date arithmetic:

1# Yesterday
2yesterday=$(date -d "yesterday" +%Y-%m-%d)
3
4# Tomorrow
5tomorrow=$(date -d "tomorrow" +%Y-%m-%d)
6
7# 7 days ago
8week_ago=$(date -d "7 days ago" +%Y-%m-%d)
9
10# 30 days from now
11future=$(date -d "+30 days" +%Y-%m-%d)
12
13# First day of current month
14first_of_month=$(date -d "$(date +%Y-%m-01)" +%Y-%m-%d)
15
16# Last day of previous month
17last_of_prev_month=$(date -d "$(date +%Y-%m-01) -1 day" +%Y-%m-%d)

BSD date (macOS)

macOS uses BSD date, which has a different syntax for date arithmetic:

1# Yesterday
2yesterday=$(date -v-1d +%Y-%m-%d)
3
4# Tomorrow
5tomorrow=$(date -v+1d +%Y-%m-%d)
6
7# 7 days ago
8week_ago=$(date -v-7d +%Y-%m-%d)
9
10# 30 days from now
11future=$(date -v+30d +%Y-%m-%d)
12
13# First day of current month
14first_of_month=$(date -v1d +%Y-%m-%d)

Cross-Platform Date Arithmetic

If your script needs to run on both Linux and macOS, detect the platform:

1#!/bin/bash
2
3get_date_offset() {
4    local days=$1
5    if date --version >/dev/null 2>&1; then
6        # GNU date (Linux)
7        date -d "$days days" +%Y-%m-%d
8    else
9        # BSD date (macOS)
10        date -v"${days}d" +%Y-%m-%d
11    fi
12}
13
14yesterday=$(get_date_offset -1)
15tomorrow=$(get_date_offset +1)
16echo "Yesterday: $yesterday"
17echo "Tomorrow: $tomorrow"

Practical Script Examples

Log Rotation with Date Stamps

1#!/bin/bash
2
3log_dir="/var/log/myapp"
4today=$(date +%Y-%m-%d)
5archive_dir="$log_dir/archive"
6
7mkdir -p "$archive_dir"
8
9# Rotate current log
10if [ -f "$log_dir/app.log" ]; then
11    mv "$log_dir/app.log" "$archive_dir/app-$today.log"
12    gzip "$archive_dir/app-$today.log"
13fi
14
15# Delete archives older than 90 days
16find "$archive_dir" -name "*.gz" -mtime +90 -delete

Timestamped Backup Script

1#!/bin/bash
2
3timestamp=$(date +%Y-%m-%d_%H-%M-%S)
4backup_dir="/backups/$timestamp"
5
6mkdir -p "$backup_dir"
7pg_dump mydb > "$backup_dir/mydb.sql"
8tar czf "$backup_dir/config.tar.gz" /etc/myapp/
9
10echo "Backup completed: $backup_dir"

Date Range Loop

Iterate over a range of dates (GNU date):

1#!/bin/bash
2
3start_date="2026-06-01"
4end_date="2026-06-18"
5
6current="$start_date"
7while [[ "$current" < "$end_date" || "$current" == "$end_date" ]]; do
8    echo "Processing $current"
9    # Your logic here
10    current=$(date -d "$current +1 day" +%Y-%m-%d)
11done

Comparing Dates

Compare dates as strings since YYYY-MM-DD format sorts lexicographically:

1#!/bin/bash
2
3today=$(date +%Y-%m-%d)
4deadline="2026-12-31"
5
6if [[ "$today" > "$deadline" ]]; then
7    echo "Deadline has passed"
8elif [[ "$today" == "$deadline" ]]; then
9    echo "Deadline is today"
10else
11    echo "Deadline is in the future"
12fi

This works because the YYYY-MM-DD format preserves chronological order in string comparison. Formats like MM/DD/YYYY do not have this property.

UTC vs. Local Time

By default, date uses the system's local timezone. For consistent results across servers in different timezones, use UTC:

1# UTC date
2utc_today=$(date -u +%Y-%m-%d)
3
4# Or set TZ explicitly
5eastern=$(TZ="America/New_York" date +%Y-%m-%d)
6tokyo=$(TZ="Asia/Tokyo" date +%Y-%m-%d)

Using UTC is especially important in cron jobs and distributed systems where servers may be in different timezones.

Format Specifier Reference

Common Pitfalls

Confusing %m with %M. %m is the month, %M is the minute. Writing date +%Y-%M-%d gives you the minute in the month position, producing nonsensical dates like 2026-30-18.

Using uppercase %D. The %D specifier produces MM/DD/YY (American short format), not YYYY-MM-DD. This is a common source of confusion.

Forgetting the + before the format string. Writing date %Y-%m-%d without the + causes date to try to parse it as a date string, not as a format specifier.

Assuming GNU date on macOS. macOS ships with BSD date, which does not support -d. Use -v for date arithmetic on macOS, or install GNU coreutils via Homebrew (gdate).

Using backticks instead of $(...). While backticks work, they do not nest cleanly and are harder to read. The $(...) syntax is the modern standard:

1# Avoid
2today=`date +%Y-%m-%d`
3
4# Prefer
5today=$(date +%Y-%m-%d)

Not quoting variables in comparisons. If the date variable is empty for any reason, an unquoted comparison like [ $today = $deadline ] will produce a syntax error. Always use double brackets or quote the variables: [[ "$today" == "$deadline" ]].

Summary

Use date +%Y-%m-%d to get the current date in ISO 8601 format in any shell script. For date arithmetic, use -d on Linux (GNU) or -v on macOS (BSD). The YYYY-MM-DD format is ideal for filenames, logs, and date comparisons because it sorts chronologically as a plain string. Use UTC (date -u) for consistent results across timezones. Watch out for the %m vs. %M confusion, and remember that macOS and Linux have different date command syntax for offsets.