Twodays: for celebrations
Is today a twoday?
Twodays bridge the gap between birthdays and anniversaries. They exist for any pair of people on dates that are unique to them. Find out when your twodays are, for you, your family, and your friends, so that you can celebrate these fun days together.
Coming soon!
Privacy
Twodays does not collect any personal data and there is no third party involvement.
What is a twoday?
Twodays can be understood by comparing them to birthdays and anniversaries.
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Birthdays are for one person. Anniversaries are for one person or two people. And twodays are for two people.
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Birthdays, anniversaries and twodays all stem from an initial event. For birthdays, this event is a birth. For anniversaries, it could be a wedding. And for twodays, it is the birth of the younger person, so that both people now exist.
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Birthdays, anniversaries and twodays all occur at regular intervals following the initial event. For birthdays and anniversaries this interval is one year, but for twodays it is instead a particular number of days. This number is calculated from the age difference between the two people. It is found by repeatedly halving, or doubling, their age difference in days, until the result lies somewhere between one and two years.
The fun thing about twodays is to do with age ratios. An age ratio is the age of one person divided by the age of the other person, where age is measured in days. At some point during a twoday it is always possible to express this age ratio as a relatively simple fraction.
For example, consider two siblings: A (the oldest) born on 1 January 2024, and B (the youngest) born on 1 January 2026. Their first twoday will be on 2 January 2027 and at some point during this day they will have an age ratio of 1/3, such that B will be exactly 1/3 the age of A. Their next twoday will be on 2 January 2008 and at some point during this day they will have an age ratio of 1/2, such that B will be exactly 1/2 the age of A.
(Assume both siblings were born at midday (12:00). Their age difference is 366 + 365 = 731 days, so the interval between their twodays is 731/2 = 365.5 days. At midnight (00:00) on 2 January 2027, A will be age 731 + 365.5 = 1096.5 days, and B will be age 365.5 days. Thus their age ratio will be 365.5/1096.5 = 1/3. At midday (12:00) on 2 January 2008, A will be age 731 + 2x365.5 = 1462 days, and B will be age 2x365.5 = 731 days. Thus their age ratio will be 731/1462 = 1/2.)
Please don't take the maths too seriously. For example, the interval between twodays could be calculated differently, which would give different twodays. It's just for fun!
Free features
Twodays is free to use for your own personal twodays. You can pair yourself with any other person and the app will be fully functional for these matches.
Twodays
Pair yourself with another person to find your next twoday, or to see all of your twodays, both past and future.
Other age ratios
No need to limit yourself to twodays. Pair yourself with another person to find the date for any age ratio you like. Anyone interested in 314/100?
Your age
Pair yourself with yourself to see your current age. You can also find your age for a particular date, and the date on which you will be a particular age. Big milestones at 10,000, 20,000 and 30,000 days old!
In-app purchase
Any two people
If you want to pair up any two people, not necessarily including yourself, then you can do this with an in-app purchase.
This purchase will also allow you to change your own name and date of birth, if you initially entered the wrong information by mistake. Oops.
Help
Please email me with any questions. I am happy to help. And suggestions are welcome too.
Happy twodays!