April 10th in a normal year or April 9th if it is a leap year.
April 10th is the 100th day of the year.
It is in April. It is the 10th in a normal year and the 9th in a leap year.
Centenary means the 100th anniversay, which would be the 100th year.
April 10th is the 100th day of this year (2009). During leap years, however, the 100th day of those years will occur on April 9th. This type of information is obtained by consulting a Julian calendar - a calendar that shows, besides normal information, the number of days which have elapsed (and usually also how many are remaining) in the current year.
It is a century or a centennial
The 9th of April was the 100th day of the year 2000.
The 100th day of the year 2012 is April 9th (because of a leap year).
9 April
In regular years, the 100th day of the year is the 10th of April. In leap years, it's the 9th of April.
The 100th day of the year is April 10, on a normal calendar year, April 9 on a leap year.
April 10th is the 100th day of the year.
April
The 100 day of the year is either April 10th - or April 9th in a leap year.
It is in April. It is the 10th in a normal year and the 9th in a leap year.
Centenary means the 100th anniversay, which would be the 100th year.
During a year that is not a leap year it is April 10. For leap years it is April 9.
Saturday the 9th of April 2016.