One Direction
ONE Direction = ONE hundred years
1D = 100Y
One Direction, an English-Irish pop boy band will celebrate 100th combine birthday 17th April 2013
Visit us on Facebook 
We are using the hashtag #1D100Y on Twitter
Combined birthday is a special birthday for two or more people. It is easy if you know your age in days. Just add up all the ages in days and divide the number of days by the number of days in a year. It is 365.2422 - tropical year. It is not 365, becouse every 4 years we have leap year. For it we have calculator, click here.
Just add up the ages of Niall, Zayn, Liam, Harry and Louis and it will be 100 years on 17th April 2013! Total combine age in days on 17th April is 36,527. 36,527 divided 365,24 is 100! You can check it on 1D calculation result.
Of course you can click on the button "Add name" and add your birthday to calculate your own combined birthday with One Direction. You can also delete the calculation using the reset button, and then choose your other favorite celebrities by clicking on star symbol 
In table below you can see haw ald are all members of 1D in days.
| Band Members | Date of Birth | Age in days 17th April 2013 | Day of Birth |
| Niall Horan | 13 September 1993 | 7,156 | Monday |
| Zayn Malik | 12 Januray 1993 | 7,400 | Tuesday |
| Liam Payne | 29 August 1993 | 7,171 | Sunday |
| Harry Styles | 1 February 1994 | 7,015 | Tuesday |
| Louis Tomlinson | 24 December 1991 | 7,785 | Tuesday |
| 36,527 total days |
Using our calculator, you can calculate so many interesting things. Below we have made a table that includes all of 1Ds milestone ages, that we can all celebrate together.
| Date | Who | What |
| 6th February 2013 | Harry | 10 milions minutes |
| 27th February 2013 | Liam | half birthday |
| 14th March 2013 | Naill | half birthday |
| 2nd April 2013 | Harry | 1000 weeks, 7000 days |
| 17th April 2013 | All 1D | 100th combined birthday |
| 27th April 2013 | Liam and Louis | 41th combined birthday |
| 3rd May 2013 | Niall and Louis | 41th combined birthday |
| 9th May 2013 | Zayn and Liam | 40th combined birthday |
| 9th May 2013 | Harry | 80th planet Mercury age |
| 13th May 2013 | Niall and Zayn | 40th combined birthday |
| 17th May 2013 | Liam and Harry | 39th combined birthday |
| 23th May 2013 | Niall and Harry | 39th combined birthday |
| 25th Jun 2013 | Louis | half birthday |
| 2nd Jul 2013 | Zayn | 85th planet Mercury age |
| 4th Jul 2013 | Zayn and Louis | 42th combined birthday |
| 5th Jul 2013 | Louis | 35th planet Venus age |
| 14th Jul 2013 | Zayn | half birthday |
| 14th Jul 2013 | Harry and Louis | 41th combined birthday |
| 24th Jul 2013 | Zayn and Harry | 40th combined birthday |
| 3nd August 2013 | Harry | half birthday |
| 5th August 2013 | Niall and Liam | 40th combined birthday |
Our coments:
We would like to celebrate 1Ds birthday. We asked mum if we could use face paints. It was fun. We would like do it again on 17th April, but it is Wednesday and we have to go 
to school. Maybe we can do painting only on our hands. Please, could you share with your friends this information about 1D celebrating 100 years. On their combined birthday, 17th April they have a concert in Birmingham. If you are going to that concert, please could you tell 1D Happy birthday for us! Thank you. We can not go to 1D concerts yet, maybe when we are older!
Dominik 10y and Martina 8y
I hope you like our webpage and all of the fun celebrations about 1D. I am working with my friend on this calculator for more than 2 years and there is still a lot more to do. If you have some comments, feel free to email me on dom@birthdaycalculators.com. Find out more about me, the calculator or who is helping me. Some information is slightly old. Now I am 10 years old and my younger sister Martina is helping me. She is very good at spelling and helps with writing articles.
Dominik
The picture of 1D used in this article has been found in Google as usage rights: "free to use, share or modifmutiationy, even commercially". Also the same picture is used in Wikipedia in many languages about 1D.