Time

In search of the perfect date...

Nice post about time:

• https://ourworldindata.org/time-use

Calculate the day of the week

Calculate a number for each of the day, month, and year by adding the digits together as follows:

In this example todays date is 15. June 2023:

Day = just todays day e.g. 15 of June

Month = the number of below table e.g. for June = 3

Years = the number of below table e.g. for 2023 = 0

When calculating the year, either memorize the table or calculate the value using the last two digits e.g. for 2023 = 23. Take 23, divide it by 4, and round down, then add it back to itself. Eg. 23/4 = 5 (rounded down). Adding this to itself we get 28 (23+5). Now, we get the remainder after dividing by 7. In our case of 28, the remainder after division by 7 is 0.

If the year is in the 20th century (1900-1999), add +1. The algorithm will not work for dates before 1582. In our example we add 0. For other centuries use this overview:

If the date is January or February of a leap year, then subtract 1 to the final answer. Here is a list of leap years from 1804-2400:

So finally, in our example we add 15+3+0+0+0 = 18 and get the remainder when dividing the result by 7 = 4.

According to the table below 4 = Thursday so 15. June 2023 was a Thursday :)

The full formula looks like this:

Remainder of (Day + Month(Table) + Year(Table) + Century + (if leap year + 1))/7 = value to look up in day of the week table.

Time zone

Some links to time zone standards:

• ISO 8601 Wikipedia https://en.wikipedia.org/wiki/ISO_8601
• ISO 8601 https://www.iso.org/obp/ui/#iso:std:iso:8601:-1:ed-1:v1:en
• ISO Weekdate Wikipedia https://en.wikipedia.org/wiki/ISO_week_date
• RFC 3339 https://tools.ietf.org/html/rfc3339
• Extended Date/Time Format (EDTF): https://www.loc.gov/standards/datetime/

A list of time zones:

Lunar Standard Time (LST)

The Lunar year consists of twelve days, named after the first men who walked on the Moon. Each day is divided into 30 cycles of time, with each cycle being divided into 24 moon-hours. Each moon-hour then has 60 moon-minutes, which in turn of course are made up of 60 moon-seconds each. The inverted triangle ∇ is the LST symbol, and if used it suffixes date and prefixes time. The standard notation is: Year-Day-Cycle ∇ Hour:Minute:Second example: 55-11-14 ∇ 14:36:49

*Each is day named after one of the twelve men that walked on the Moon during the Apollo projects:

On the moon you have about 15 days of continuous daylight and then 15 days of total darkness. So, a "day" on the Moon, would correspond to about a month or 29.5 Earth-days. Once, about every 29 days, you have a full moon, which is "noon" on the center of the disk. This is also called the synodic month. So a day on the moon, counting from noon to noon, lasts about 29.27 to 29.83 Earth days. Neil Armstrong set foot on the Moon surface on July 21th 1969 at 02:56:15 UT, and this is the obvious choice for a point in time for the calendar to start. So, this is Year 1, day 1 cycle 1, 00:00:00.

Metric Time

Sources:

• https://en.wikipedia.org/wiki/Metric_time
• https://timeity.com/metric-time/

Calendar

List of calendars: https://en.wikipedia.org/wiki/List_of_calendars

Representation in various calendars of the year 2021

Non 7-day weeks

Age

Korean Age vs. International Age

In South Korea, the method of calculating age diverges from the norm observed in most countries. Grasping the distinction between Korean and international age is vital for those engaging with Korean culture. Upon birth, Koreans are already considered a year old, reflecting the time in the womb. Furthermore, every individual's age advances by a year on New Year's Day, irrespective of their actual birth date. Consequently, a Korean's age is consistently one to two years greater than their international counterpart.

The international age system, adopted by the majority of countries, increments a person's age annually on their birthday. By June 2023, to mitigate confusion, the Korean government resolved to exclusively use the international age system for official and legal documentation. This shift means Koreans' official age will now be one to two years less than what's calculated using the traditional Korean method.

In Korean culture, age profoundly influences social dynamics, language nuances, and societal expectations. For example, it's customary for younger individuals to pour drinks, while their elders often cover meal expenses. Inquiring about age in Korea varies based on the individual's age and one's relationship with them, with distinct formal, standard, and informal phrasings. Legal age thresholds, such as for alcohol consumption, align with the international age system. To illustrate, while the Korean age for legal drinking is 20, it translates to 19 in international terms. Though Koreans universally age up on January 1st, personal birthday celebrations occur on the actual date of birth. When two Koreans are of the same age, they refer to their peer relationship as "동갑 (donggap)." This age parity often eases interactions, eliminating the usual age-related social protocols.

Calculating Korean Age:

Calculating Korean age is relatively straightforward. Here's how you can determine someone's Korean age:

• Start with the Current Year: Begin by taking the current year. For example, if it's 2023, start with that number.
• Subtract the Birth Year: Deduct the person's birth year from the current year.
• Add One Year: Since in Korea, a baby is considered one year old at birth (accounting for the time spent in the womb), you add one year to the result from step 2.

For example, if someone was born in 2000 and the current year is 2023:

2023 (current year) - 2000 (birth year) = 23 23 + 1 = 24

So, the person's Korean age in 2023 would be 24.

However, there's one more thing to consider: New Year's Adjustment: Everyone's age in Korea increases by one year on New Year's Day, regardless of their actual birth date. This means if someone's birthday hasn't occurred yet in the current year, their Korean age will be two years more than their international age. Using the example above, if the person's birthday is in July and it's currently February 2023, they would still be 23 in international age but 24 in Korean age.

In summary, the formula is:

Korean Age = (Current Year - Birth Year) + 1

Remember the New Year's adjustment when considering birthdays later in the year.

Fun facts

A moment was a medieval unit of time. The movement of a shadow on a sundial covered 40 moments in a solar hour. An hour in this case meant one twelfth of the period between sunrise and sunset. The length of a solar hour depended on the length of the day, which in turn varied with the season, so the length of a moment in modern seconds was not fixed, but on average, a moment corresponded to 90 seconds.

Fictional calendars

• Discworld
• Middle-earth
• Star Trek (Stardates)

Links

• 120 years of timezones: https://blog.scottlogic.com/2021/09/14/120-years-timezone.html
• https://en.wikipedia.org/wiki/ISO_3166-1
• https://www.timeanddate.com/time/zones/
• https://www.iana.org/time-zones
• https://www.ibm.com/docs/en/workload-scheduler/8.6.0?topic=zones-complete-table-time-variable-length-notation

Wikipedia on time, calendars and dates

• https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
• https://en.wikipedia.org/wiki/List_of_dates_predicted_for_apocalyptic_events
• https://en.wikipedia.org/wiki/List_of_unusual_units_of_measurement#Time
• https://en.wikipedia.org/wiki/Soviet_calendar
• https://en.wikipedia.org/wiki/Hanke%E2%80%93Henry_Permanent_Calendar