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Age Calculator

Just enter the birthday you wish to track and JavaScript will display the person's age, down to the second. Displays your age along with the day you were born.

Sample:
Click here for demo!

Replace <body> with <body onLoad="start()">

Insert this code before </head>

<SCRIPT LANGUAGE="JavaScript">

<!-- Begin
function start() {
document.form1.day.value = "";
document.form1.month.value = "";
document.form1.year.value = "";
document.form1.age.value = "";
document.form1.months.value = "";
document.form1.weeks.value = "";
document.form1.answer.value = "";
document.form1.hours.value = "";
document.form1.min.value = "";
document.form1.sec.value = "";
document.form1.bday.value = "";
document.form1.milli.value = "";
}
function run() {
var ap;
dd = document.form1.day.value;
mm = document.form1.month.value;
yy = document.form1.year.value;
with(document.form1) {
ap = parseInt(ampm.selectedIndex);
hr = parseInt(hrs.value);
if(hr <= 0 && hr >= 13) {
ap = null;
alert("asdf")
   }
}
main="valid";
if ((mm < 1) || (mm > 12) || (dd < 1) || (dd > 31) || (yy < 1) ||(mm == "") || (dd == "") || (yy == ""))
main = "Invalid";
else
if (((mm == 4) || (mm == 6) || (mm == 9) || (mm == 11)) && (dd > 30))
main = "Invalid";
else
if (mm == 2) {
if (dd > 29)
main = "Invalid";
else if((dd > 28) && (!lyear(yy)))
main="Invalid";
}
else
if((yy > 9999)||(yy < 0))
main = "Invalid";
else
main = main;
if(main == "valid") {
function leapyear(a) {
if(((a % 4 == 0) && (a % 100 != 0)) || (a % 400 == 0))
return true;
else
return false;
}
days = new Date();
gdate = days.getDate();
gmonth = days.getMonth();
gyear = days.getYear();
age = gyear - yy;
if((mm == (gmonth + 1)) && (dd <= parseInt(gdate))) {
age = age;
}
else {
if(mm <= (gmonth)) {
age = age;
}
else {
age = age - 1;
   }
}
if(age == 0)
age = age;
document.form1.age.value="  You are " + age+ " years old   &  ";
if(mm <= (gmonth + 1))
age = age - 1;
if((mm == (gmonth + 1)) && (dd > parseInt(gdate)))
age = age + 1;
var m;
var n;
if (mm == 12) { n = 31 - dd; }
if (mm == 11) { n = 61 - dd; }
if (mm == 10) { n = 92 - dd; }
if (mm == 9) { n = 122 - dd; }
if (mm == 8) { n = 153 - dd; }
if (mm == 7) { n = 184 - dd; }
if (mm == 6) { n = 214 - dd; }
if (mm == 5) { n = 245 - dd; }
if (mm == 4) { n = 275 - dd; }
if (mm == 3) { n = 306 - dd; }
if (mm == 2) { n = 334 - dd; if(leapyear(yy)) n = n + 1; }
if (mm == 1) { n = 365 - dd; if (leapyear(yy)) n = n + 1; }
if (gmonth == 1) m = 31;
if (gmonth == 2) { m = 59;   if (leapyear(gyear)) m = m + 1; }
if (gmonth == 3) { m = 90;   if (leapyear(gyear)) m = m + 1; }
if (gmonth == 4) { m = 120;  if (leapyear(gyear)) m = m + 1; }
if (gmonth == 5) { m = 151;  if (leapyear(gyear)) m = m + 1; }
if (gmonth == 6) { m = 181;  if (leapyear(gyear)) m = m + 1; }
if (gmonth == 7) { m = 212;  if (leapyear(gyear)) m = m + 1; }
if (gmonth == 8) { m = 243;  if (leapyear(gyear)) m = m + 1; }
if (gmonth == 9) { m = 273;  if (leapyear(gyear)) m = m + 1; }
if (gmonth == 10) { m = 304; if (leapyear(gyear)) m = m + 1; }
if (gmonth == 11) { m = 334; if (leapyear(gyear)) m = m + 1; }
if (gmonth == 12) { m = 365; if (leapyear(gyear)) m = m + 1; }
totdays = (parseInt(age) * 365);
totdays += age / 4;
totdays = parseInt(totdays) + gdate + m + n;
document.form1.answer.value = "" + totdays +" days ";
months = age * 12;
months += 12 - parseInt(mm);
months += gmonth;
document.form1.months.value = months + " Months";
if (gmonth == 1) p = 31 + gdate;
if (gmonth == 2) { p = 59 + gdate;   if (leapyear(gyear)) m = m + 1; }
if (gmonth == 3) { p = 90 + gdate;   if (leapyear(gyear)) p = p + 1; }
if (gmonth == 4) { p = 120 + gdate;  if (leapyear(gyear)) p = p + 1; }
if (gmonth == 5) { p = 151 + gdate;  if (leapyear(gyear)) p = p + 1; }
if (gmonth == 6) { p = 181 + gdate;  if (leapyear(gyear)) p = p + 1; }
if (gmonth == 7) { p = 212 + gdate;  if (leapyear(gyear)) p = p + 1; }
if (gmonth == 8) { p = 243 + gdate;  if (leapyear(gyear)) p = p + 1; }
if (gmonth == 9) { p = 273 + gdate;  if (leapyear(gyear)) p = p + 1; }
if (gmonth == 10) { p = 304 + gdate; if (leapyear(gyear)) p = p + 1; }
if (gmonth == 11) { p = 334 + gdate; if (leapyear(gyear)) p = p + 1; }
if (gmonth == 12) { p = 365 + gdate; if (leapyear(gyear)) p = p + 1; }
weeks = totdays / 7;
weeks += " weeks";
weeks = parseInt(weeks);
document.form1.weeks.value = weeks + " Weeks";
var time = new Date();
ghour = time.getHours();
gmin = time.getMinutes();
gsec = time.getSeconds();
hour = ((age * 365) + n + p) * 24;
hour += (parseInt(age / 4) * 24);
if(ap == 0)
hour = hour - hr;
else {
if(ap == 1) {
hour = hour - (11 + hr)
   }
}
document.form1.hours.value = hour + " Hours";
var min;
min = (hour * 60) + gmin;
document.form1.min.value = min + " Minutes";
sec = (min * 60) + gsec;
document.form1.sec.value = sec + " Seconds";
var millisec;
var gmil;
gmil = days.getMilliseconds();
millisec = (sec * 1000) + gmil;
document.form1.milli.value = millisec + " Milliseconds";
mm = mm - 1;
var r;
if(mm == 0) r = 1;
if(mm == 1) r = 31;
if(mm == 2) { r = 59;    if (leapyear(gyear)) m = m + 1; }
if(mm == 3) { r = 90;    if (leapyear(gyear)) r = r + 1; }
if(mm == 4) { r = 120;   if (leapyear(gyear)) r = r + 1; }
if(mm == 5) { r = 151;   if (leapyear(gyear)) r = r + 1; }
if(mm == 6) { r = 181;   if (leapyear(gyear)) r = r + 1; }
if(mm == 7) { r = 212;   if (leapyear(gyear)) r = r + 1; }
if(mm == 8) { r = 243;   if (leapyear(gyear)) r = r + 1; }
if(mm == 9) { r = 273;   if (leapyear(gyear)) r = r + 1; }
if(mm == 10) { r = 304;  if (leapyear(gyear)) r = r + 1; }
if(mm == 11) { r = 334;  if (leapyear(gyear)) r = r + 1; }
if(mm == 12) { r = 365;  if (leapyear(gyear)) r = r + 1; }
mm = mm + 1;
r = parseInt(r) + parseInt(dd);
if( mm > (gmonth + 1)) {
bday = r - m - gdate;
}
else {
if(mm == (gmonth + 1) && (gdate < dd)) {
bday = (r - m - gdate);
}
else {
if((leapyear(gyear)) && ((mm > 2) && (dd < 29))) {
a = 366;
}
else {
a = 365;
}
bday = a + (r - m - gdate);
   }
}
nhour = 24-parseInt(ghour);
nmin = 60 - parseInt(gmin);
nsec = 60 - parseInt(gsec);
go();
if(((bday == 366) && (leapyear(yy))) || ((bday == 365) && (!leapyear(yy)))) {
document.form1.bday.value = "today is your birthday";
alert("Happy Birthday");
} else {
document.form1.bday.value = bday + " days " + nhour + " hours " + nmin + " minutes " + nsec + " seconds";
setTimeout("run()", 1);
}
function go() {
function lyear(a) {
if(((a % 4 == 0) && (a % 100 != 0)) || (a % 400 == 0)) return true;
else return false;
}
mm = parseInt(mm);
dd = parseInt(dd);
yy = parseInt(yy);
if ((mm < 1) || (mm > 12) || (dd < 1) || (dd > 31) || (yy < 1) ||(mm == " ") || (dd == " ") || (yy == " "))  main="Invalid";
else
if (((mm == 4) || (mm == 6) || (mm == 9) || (mm == 11)) && (dd > 30)) main = "Invalid";
else
if (mm == 2) {
if (dd > 29)
main = "Invalid";
else
if(( dd > 28) && (!lyear(yy)))
main = "Invalid";
}
else main = main;
if(main == "valid") {
var m;
if (mm == 1) n = 31;
if (mm == 2) n = 59 + 1;
if (mm == 3) n = 90 + 1;
if (mm == 4) n = 120 + 1;
if (mm == 5) n = 151 + 1;
if (mm == 6) n = 181 + 1;
if (mm == 7) n = 212 + 1;
if (mm == 8) n = 243 + 1;
if (mm == 9) n = 273 + 1;
if (mm == 10) n = 304 + 1;
if (mm == 11) n = 334 + 1;
if (mm == 12) n = 365 + 1;
if((mm == 1)||(mm == 3)||(mm == 5)||(mm == 7)||(mm == 8)||(mm == 10)||(mm == 12))
n += 31 + dd;
else if((mm == 4)||(mm == 6)||(mm == 9)||(mm == 11))
n += 31 + dd + 1;
else if(mm == 2) {
if(lyear(yy)) n += 29 + dd - 3;
else if(!lyear(yy)) n += 28 + dd - 1;
}
fours = yy / 4;
hunds = yy / 100;
fhunds = yy / 400;
var day;
day = (yy + n + fours - hunds + fhunds) % 7;
day = parseInt(day)
switch(day)
{
case 1 : document.form1.age.value +="  you were born on a  Sunday"
break
case 2 : document.form1.age.value +="  you were born on a  Monday"
break
case 3 : document.form1.age.value +="  you were born on a  Tuesday"
break
case 4 : document.form1.age.value +="  you were born on a  Wednesday"
break
case 5 : document.form1.age.value +="  you were born on a  Thursday"
break
case 6 : document.form1.age.value +="  you were born on a  Friday"
break
case 7 : document.form1.age.value +="  you were born on a  Saturday"
break
case 0 : document.form1.age.value +="  you were born on a  Saturday"
break
   }
}
else {
document.form1.age.value += main + " Date";
      }
   }
}
else {
document.form1.age.value = main + " Date";
document.form1.months.value = "";
document.form1.weeks.value = "";
document.form1.answer.value = "";
document.form1.hours.value = "";
document.form1.min.value = "";
document.form1.sec.value = "";
document.form1.bday.value = "";
document.form1.milli.value = "";
   }
}
//  End -->
</script>

Insert this code before </body>

<CENTER>
<br>
Enter your date of birth
<br>
<FORM name=form1>
Month<INPUT name=month size=3>
Date<INPUT name=day size=3>
Year<INPUT name=year size=6>
Hours<INPUT name=hrs value=00 size=6>
<select size="1" name="ampm">
<option selected>AM</option>
<option>PM</option>
</select>
<INPUT name=start onclick=run() type=button value="Calculate">
<BR>
<BR>
<INPUT name=age size=55 value="Your age will be displayed here">
<BR>
<BR>
You have been living for:
<BR>
<TABLE border = 0>
<TBODY>
<TR>
<TD>In months:</TD>
<TD><INPUT name=months size=30></TD>
</TR>
<TR>
<TD>In weeks:</TD>
<TD><INPUT name=weeks size=30></TD>
</TR>
<TR>
<TD>In days:</TD>
<TD><INPUT name=answer size=30></TD>
</TR>
<TR>
<TD>In hours:</TD>
<TD><INPUT name=hours size=30></TD>
</TR>
<TR>
<TD>In minutes:</TD>
<TD><INPUT name=min size=30></TD>
</TR>
<TR>
<TD>In seconds:</TD>
<TD><INPUT name=sec size=30></TD>
</TR>
<TR>
<TD>In Milliseconds:</TD>
<TD><INPUT name=milli size=30></TD>
</TR>
</TBODY>
</TABLE>
Your next birthday will be in:
<BR>
<INPUT name=bday size=40>
</FORM>
</CENTER>

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