tmpltool 1.5.0

# Date and Time Functions Demonstration
# ========================================

{% set test_timestamp = 1704067200 %}
{% set test_timestamp2 = 1704153600 %}

## Date Formatting

### format_date() - Format Unix timestamps

Default format:
{{ format_date(timestamp=test_timestamp) }}

Custom formats:
  ISO date:        {{ format_date(timestamp=test_timestamp, format="%Y-%m-%d") }}
  US format:       {{ format_date(timestamp=test_timestamp, format="%m/%d/%Y") }}
  Full month:      {{ format_date(timestamp=test_timestamp, format="%B %d, %Y") }}
  With time:       {{ format_date(timestamp=test_timestamp, format="%Y-%m-%d %H:%M:%S") }}
  12-hour format:  {{ format_date(timestamp=test_timestamp, format="%I:%M %p") }}
  Day of week:     {{ format_date(timestamp=test_timestamp, format="%A, %B %d, %Y") }}

## Date Parsing

### parse_date() - Parse date strings to Unix timestamps

{% set parsed = parse_date(string="2024-01-01 12:00:00", format="%Y-%m-%d %H:%M:%S") %}
Parsed timestamp: {{ parsed }}
Verify: {{ format_date(timestamp=parsed) }}

Parse US format:
{% set us_date = parse_date(string="12/25/2024", format="%m/%d/%Y") %}
  Input: 12/25/2024
  Output: {{ format_date(timestamp=us_date, format="%Y-%m-%d") }}

## Date Arithmetic

### date_add() - Add/subtract days

Original: {{ format_date(timestamp=test_timestamp, format="%Y-%m-%d") }}
  +7 days:  {{ format_date(timestamp=date_add(timestamp=test_timestamp, days=7), format="%Y-%m-%d") }}
  +30 days: {{ format_date(timestamp=date_add(timestamp=test_timestamp, days=30), format="%Y-%m-%d") }}
  -7 days:  {{ format_date(timestamp=date_add(timestamp=test_timestamp, days=-7), format="%Y-%m-%d") }}
  +365 days: {{ format_date(timestamp=date_add(timestamp=test_timestamp, days=365), format="%Y-%m-%d") }}

### date_diff() - Calculate difference in days

Date 1: {{ format_date(timestamp=test_timestamp, format="%Y-%m-%d") }}
Date 2: {{ format_date(timestamp=test_timestamp2, format="%Y-%m-%d") }}
Difference: {{ date_diff(timestamp1=test_timestamp2, timestamp2=test_timestamp) }} days

## Date Component Extraction

Timestamp: {{ test_timestamp }} ({{ format_date(timestamp=test_timestamp) }})

  Year:   {{ get_year(timestamp=test_timestamp) }}
  Month:  {{ get_month(timestamp=test_timestamp) }}
  Day:    {{ get_day(timestamp=test_timestamp) }}
  Hour:   {{ get_hour(timestamp=test_timestamp) }}
  Minute: {{ get_minute(timestamp=test_timestamp) }}

## Timezone Conversion

### timezone_convert() - Convert between timezones

UTC timestamp: {{ test_timestamp }}
  UTC time:     {{ format_date(timestamp=test_timestamp, format="%Y-%m-%d %H:%M:%S %Z") }}

Note: timezone_convert returns the same Unix timestamp, but it's useful when
formatting times in different timezones. Unix timestamps are timezone-independent.

## Leap Year Check

### is_leap_year() - Check if a year is a leap year

{% set years = [2020, 2021, 2022, 2023, 2024, 2000, 1900, 2100] %}
{% for year in years %}
  {{ year }}: {% if is_leap_year(year=year) %}Leap Year ✓{% else %}Not a Leap Year ✗{% endif %}
{% endfor %}

## Real-World Use Cases

### 1. Log File Rotation
```yaml
{% set now_ts = parse_date(string="2024-12-31 14:30:00", format="%Y-%m-%d %H:%M:%S") %}
logs:
  current: /var/log/app.log
  archive:
    {% for day_offset in range(1, 8) %}
    - /var/log/app-{{ format_date(timestamp=date_add(timestamp=now_ts, days=-day_offset), format="%Y%m%d") }}.log
    {% endfor %}
```

### 2. Backup Schedule
```bash
#!/bin/bash
{% set backup_ts = parse_date(string="2024-01-15 02:00:00", format="%Y-%m-%d %H:%M:%S") %}
# Backup schedule for January 2024

# Full backup (1st of month)
FULL_BACKUP_DATE="{{ format_date(timestamp=parse_date(string="2024-01-01", format="%Y-%m-%d"), format="%Y-%m-%d") }}"

# Weekly backups
{% for week in range(0, 4) %}
WEEKLY_BACKUP_{{ week + 1 }}="{{ format_date(timestamp=date_add(timestamp=backup_ts, days=week * 7), format="%Y-%m-%d") }}"
{% endfor %}

# Retention: Keep backups for 30 days
{% set retention_cutoff = date_add(timestamp=backup_ts, days=-30) %}
DELETE_BEFORE="{{ format_date(timestamp=retention_cutoff, format="%Y-%m-%d") }}"
```

### 3. Event Countdown
```yaml
{% set event_date = parse_date(string="2024-12-25", format="%Y-%m-%d") %}
{% set today = parse_date(string="2024-01-01", format="%Y-%m-%d") %}
{% set days_until = date_diff(timestamp1=event_date, timestamp2=today) %}

event:
  name: "Christmas 2024"
  date: {{ format_date(timestamp=event_date, format="%B %d, %Y") }}
  countdown: {{ days_until }} days remaining
  is_this_year: {{ get_year(timestamp=event_date) == get_year(timestamp=today) }}
```

### 4. Lease/Subscription Expiration
```yaml
{% set start_date = parse_date(string="2024-01-01", format="%Y-%m-%d") %}
{% set duration_days = 365 %}
{% set end_date = date_add(timestamp=start_date, days=duration_days) %}
{% set check_date = parse_date(string="2024-06-15", format="%Y-%m-%d") %}
{% set days_remaining = date_diff(timestamp1=end_date, timestamp2=check_date) %}

subscription:
  start_date: {{ format_date(timestamp=start_date, format="%Y-%m-%d") }}
  end_date: {{ format_date(timestamp=end_date, format="%Y-%m-%d") }}
  duration: {{ duration_days }} days ({{ is_leap_year(year=get_year(timestamp=start_date)) and "leap year" or "regular year" }})

  status:
    check_date: {{ format_date(timestamp=check_date, format="%Y-%m-%d") }}
    days_remaining: {{ days_remaining }}
    {% if days_remaining > 30 %}
    status: active
    {% elif days_remaining > 0 %}
    status: expiring_soon
    renewal_reminder: true
    {% else %}
    status: expired
    {% endif %}
```

### 5. Cron Schedule Generator
```cron
# Generated on {{ format_date(timestamp=parse_date(string="2024-01-01", format="%Y-%m-%d"), format="%Y-%m-%d") }}

# Daily backup at 2 AM
0 2 * * * /usr/local/bin/backup-daily.sh

# Weekly full backup (Sundays at 3 AM)
0 3 * * 0 /usr/local/bin/backup-full.sh

{% set cleanup_day = get_day(timestamp=date_add(timestamp=parse_date(string="2024-01-01", format="%Y-%m-%d"), days=30)) %}
# Monthly cleanup (day {{ cleanup_day }} at 4 AM)
0 4 {{ cleanup_day }} * * /usr/local/bin/cleanup-old-backups.sh
```

### 6. Certificate Expiration Warning
```yaml
{% set cert_expiry = parse_date(string="2025-06-15", format="%Y-%m-%d") %}
{% set today = parse_date(string="2024-12-31", format="%Y-%m-%d") %}
{% set days_until_expiry = date_diff(timestamp1=cert_expiry, timestamp2=today) %}

certificates:
  ssl_cert:
    expires: {{ format_date(timestamp=cert_expiry, format="%B %d, %Y") }}
    days_remaining: {{ days_until_expiry }}
    {% if days_until_expiry < 30 %}
    warning: "Certificate expires in {{ days_until_expiry }} days - RENEW IMMEDIATELY"
    priority: critical
    {% elif days_until_expiry < 90 %}
    warning: "Certificate expires in {{ days_until_expiry }} days - schedule renewal"
    priority: high
    {% else %}
    status: valid
    priority: normal
    {% endif %}
```

## Format Specifiers Reference

Common format codes for format_date():
  %Y - Year (4 digits)          Example: 2024
  %m - Month (01-12)            Example: 01
  %d - Day (01-31)              Example: 15
  %H - Hour 24h (00-23)         Example: 14
  %I - Hour 12h (01-12)         Example: 02
  %M - Minute (00-59)           Example: 30
  %S - Second (00-59)           Example: 45
  %p - AM/PM                    Example: PM
  %A - Weekday (full)           Example: Monday
  %a - Weekday (abbr)           Example: Mon
  %B - Month (full)             Example: January
  %b - Month (abbr)             Example: Jan

Full reference: https://docs.rs/chrono/latest/chrono/format/strftime/index.html