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Published on: Saturday 11th October 1997 By: Martin Webb
This article will describe how to calculate the age in years, months and days of someone who supplies their birthdate.
It will use the date input routines described in the previous article Blind Date.
The following HowOld() function works out the difference between the two dates represented by day, month, year and thisDay, thisMonth, thisYear.
The HowOld() function relies on the first date being older than the second date.
It uses simple addition and subtraction to calculate the difference, using borrowing to borrow from yearsold and monthsold where month is greater than thisMonth and where day is greater then thisDay.
It returns an empty string if either the resulting yearsold is negative, or if yearsold, monthsold and daysold are all zero.
It finally returns a formatted string along the lines of: Age - 3 years 2 months 1 day
function HowOld(day,month,year,thisDay,thisMonth,thisYear) {
var yearsold = thisYear - year, monthsold = 0, daysold = 0, string = '';
if (thisMonth >= month) monthsold = thisMonth - month;
else { yearsold--; monthsold = thisMonth + 12 - month; }
if (thisDay >= day)daysold = thisDay - day;
else {
if (monthsold > 0) monthsold--;
else { yearsold--; monthsold+=11; }
daysold = thisDay + 31 - day;
}
if (yearsold < 0) return '';
if ((yearsold == 0) && (monthsold == 0) && (daysold == 0))
return '';
if (yearsold > 0) {
string = yearsold + ' year';
if (yearsold > 1) string += 's';
string += ' ';
}
if (monthsold > 0) {
string += monthsold + ' month';
if (monthsold > 1) string += 's';
string += ' ';
}
if (daysold > 0) {
string += daysold + ' day';
if (daysold > 1) string += 's';
string += ' ';
}
return '<P>Age - ' + string;
}The HowOld() function can be utilised as follows:
document.write(HowOld(1,1,1900,4,10,1997));
Which when run produces:
Note, the above is not 100% accurate as it assumes that every month has 31 days.
Why not try it out the frame version yourself. You may be older than you think!
You can view the source code of the four components:
Extending "Born of the 4th of July"
Monday's child is full of grace