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This date falls on:
Sunday, February 15, 2026
Origin
Planet
ISO Day Number
7
0 Calendar
ISO 8601 International Standard
What is ISO 8601?
ISO 8601 is the international standard maintained by the International Organization for Standardization (ISO) that governs the worldwide exchange of date and time-related data. It establishes Monday as the official first day of the week.
Week Numbering
According to ISO 8601, weeks start on Monday (day 1) and end on Sunday (day 7). This standard is widely adopted by developed countries and international organizations for consistency in business, technology, and communication.
Day Numbers: Monday = 1, Tuesday = 2, Wednesday = 3, Thursday = 4, Friday = 5, Saturday = 6, Sunday = 7
The Gregorian Calendar
Origin and Purpose
Named after Pope Gregory XIII, the Gregorian Calendar is based on Earth's revolution around the Sun (approximately one year) and the Moon's orbit around Earth (roughly one month). It was introduced in 1582 to correct drift in the Julian calendar.
Modern Usage
Today, the Gregorian calendar is the most widely used civil calendar worldwide. It refined ancient timekeeping methods that used celestial bodies to measure time, creating the 365-day year with leap years every four years to maintain accuracy.
Origins of Weekday Names
The names of weekdays derive from ancient Roman gods and celestial bodies during the Hellenistic period (323 BC - 31 BC). These names spread through Latin culture and influenced languages worldwide, from French and German to Japanese and Indian languages.
Sunday
Roman Origin: Sol (Sun God)
Celestial Body: Sun
Monday
Roman Origin: Luna (Moon)
Celestial Body: Moon
Tuesday
Roman Origin: Mars (War God)
Celestial Body: Mars
Wednesday
Roman Origin: Mercury (Messenger)
Celestial Body: Mercury
Thursday
Roman Origin: Jupiter (Thunder)
Celestial Body: Jupiter
Friday
Roman Origin: Venus (Love)
Celestial Body: Venus
Saturday
Roman Origin: Saturn (Time)
Celestial Body: Saturn
Cultural Differences
Weekend Variations
- Western countries: Saturday and Sunday
- Middle East: Friday and Saturday (or Thursday and Friday)
- Israel: Friday afternoon through Saturday
- Some Islamic countries: Thursday and Friday
Week Start Day
- ISO 8601 / Most of Europe: Monday
- United States / Canada: Sunday
- Middle Eastern countries: Saturday or Sunday
- International business: Monday (ISO standard)
Why It Matters
Everyday Uses
- Planning events and meetings across time zones
- Calculating historical dates for research
- Scheduling recurring appointments
- Understanding birth days and anniversaries
- Coordinating international business operations
Fun Applications
- Find out what day you were born on
- Calculate what day future dates will fall on
- Discover historical event days
- Plan special celebrations strategically
Quick Reference Guide
Common Patterns
- • Months starting on Sunday have Friday the 13th
- • Every 400 years, calendar patterns repeat
- • Leap years occur every 4 years (with exceptions)
- • A year has 365 days (366 in leap years)
Days Per Month
- • 31 days: Jan, Mar, May, Jul, Aug, Oct, Dec
- • 30 days: Apr, Jun, Sep, Nov
- • 28/29 days: February (leap year)
- • Mnemonic: "30 days hath September..."
Historical Notes
- • Gregorian calendar adopted in 1582
- • Replaced the Julian calendar
- • ISO 8601 established in 1988
- • Used by over 99% of the world