reverse-month

christopheryeo

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About

This skill converts dates from various formats to a standardized YYYY-MM (ISO year-month) format. It's useful for extracting month components, standardizing date formats, and preparing data for monthly aggregations and reporting. The tool handles flexible date parsing and outputs consistent machine-readable month values.

Quick Install

Claude Code

Recommended

Plugin CommandRecommended

/plugin add https://github.com/christopheryeo/claude-skills

Git CloneAlternative

git clone https://github.com/christopheryeo/claude-skills.git ~/.claude/skills/reverse-month

Copy and paste this command in Claude Code to install this skill

Documentation

Reverse Month Converter

Overview

Convert dates from various human-readable formats into standardized "reverse month" format (YYYY-MM). This skill handles flexible date input parsing and provides consistent, machine-readable month output by extracting only the year and month components from a full date.

The reverse month format is the year and month portion of an ISO date (YYYY-MM), making it ideal for monthly reporting, time-series aggregations, and calendar operations.

Usage

Use the convert_month.py script to convert any date string to YYYY-MM format:

python scripts/convert_month.py "21 Oct 2025"
# Output: 2025-10

Supported Input Formats

The script accepts a wide variety of date formats, including:

Month-day-year: "21 Oct 2025", "October 21, 2025", "Oct 21, 2025"
Slash-separated: "21/10/2025", "10/21/2025"
Dash-separated: "21-10-2025", "2025-10-21"
ISO format: "2025-10-21"
Other common formats: Most standard date representations

Examples

# Human-readable format
python scripts/convert_month.py "21 Oct 2025"
# → 2025-10

# Full month name
python scripts/convert_month.py "October 21, 2025"
# → 2025-10

# Slash format
python scripts/convert_month.py "21/10/2025"
# → 2025-10

# Already in ISO format
python scripts/convert_month.py "2025-10-21"
# → 2025-10

# Short format
python scripts/convert_month.py "Oct 2025"
# → 2025-10

Error Handling

If the date string cannot be parsed, the script returns an error message:

python scripts/convert_month.py "invalid date"
# Error: Unable to parse date: 'invalid date'. Error: Unknown string format: invalid date

Common Use Cases

Monthly reporting and aggregations
Calendar month filtering
Time-series data grouping by month
Standardizing month identifiers across different date formats
Extracting billing or subscription periods

Relationship to reverse-date Skill

This skill builds upon the reverse-date skill concept. While reverse-date converts dates to full ISO format (YYYY-MM-DD), reverse-month extracts only the year-month portion (YYYY-MM), providing a coarser granularity suitable for monthly operations.

Implementation Details

The script uses Python's dateutil.parser library for flexible date parsing, which handles many common date formats automatically. The output is always in ISO 8601 year-month format (YYYY-MM).

GitHub Repository

christopheryeo/claude-skills

Path: reverse-month

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