Example to go thru your User model and return all the signups by month / year, doing conditionals on them and grouping,

@users = User.find(
  :all, 
  :select => "MONTH(created_at) as month, YEAR(created_at) as year, COUNT(*) AS records",
  :conditions => ["admin = 0'"], 
  :group => "year, month")

You can use this in your view like,

<% for @user in @users %>
  <%=@user.month%>
  <%=@user.year%>
  <%=@user.records%> signups
<% end %>

Had a bit of a pain with Ruby's handling of Date/Time values coming from a Date_Select form element, managed to solve it though.

The problem was that in my form...

<%=date_select(:date,'',:start_year => 1950,:include_blank => false, :default => { :year => '1970' })%>

...the value I got back from the submitted field,

params[:date]

became...

'(3i)4(1i)1953(2i)5'

Bit of a mess, obviously I was expecting something a little more legible like 1953-5-4 (yyyy-mm-dd), so I bashed my head against a brick wall trying to work it out, I could have made my life easier with some select_date blocks but I'm a guy how likes to ask 'why' so I perceviered.

Turns out in my travels you can do this to break it into a usable DateTime object..

Time.mktime(params[:date]['(1i)'],params[:date]['(2i)'],params[:date]['(3i)'])

Which will return something much more legible...

Sun May 19 00:00:00 +0100 1968

Or whip it into a method to do exactly what you want...

def convert_date(obj)
  return "#{obj['(1i)']}-#{obj['(2i)']}-#{obj['(2i)']}"
end

<%=convert_date(params[:date])%>

But wait, it doesn't end there, you could use Date.new or Date.civil to parse it into a real date object like...

def convert_date(obj)
  return Date.new(obj['(1i)'].to_i,obj['(2i)'].to_i,obj['(3i)'].to_i)    
end

Which will return...

1967-03-19

Much nicer, just remember to use .to_i otherwise you'll get...

comparison of String with 0 failed

Enjoy!

• Ruby Dates & Times Wiki

One sometimes misunderstood element of JavaScript is how it handles dates, so in this article I'm going to try and conquer that little confusion.

P.S. Happy Christmas!!!

Dates in Depth

Returning the Current Date

Simple,

document.write(Date());

Creating a Date Object

First off you'll need to create a Date object, this is accomplished by...

var d = new Date();

This creates a new variable with the type as a date object, named d, with the default value as the current date & time.

Setting it's Value

var d = new Date("11/23/2007");

This will create a new Data object and set it's initial date to November 23rd 2007 (note it uses the American format mm/dd/yyyy).

You can set it's date afterwards with the .setFullYear();

d.setFullYear(1997,11,3);

Using the format YYYY/MM/DD.

Days

To return the day value of a Date object do,

document.write(d.getDate());  
// returns => 23 from 23rd Nov 2006
// (1..31)

document.write(d.getDay());   
// returns day of week value lands on, e.g. 2 for Monday for 23rd
// (0..6)

Yes this can be confusing, getDay() does not return what you expect (e.g. 23 from 11/23/2007), but the numeric value for the day of the week the 23rd lands on, so if the 23rd lands on a Tuesday it'd be 3. Use getDate() to return 23.

Setting the Day

document.write(d.setDate(11));
// sets the day digit to 11

Months

To return the month value of a Date object do,

document.write(d.getMonth());
// returns values from 0..11 (0=Jan 11=Dec)
// (0..11)

Because Month is an array, you'll need to add 1 to it to return days from 1..12,

document.write(d.getMonth()+1);
// returns values from 1..12 (corrected by adding 1 to the value)

Setting the Month,

d.setMonth(mm,dd);

// e.g.
document.write(d.setMonth(11,1));
// set the month to December the 1st

Years

To return the Year value of an Date object do,

document.write(d.getFullYear());
// returns 2007 for 11/23/2007

Note, there was a function called getYear() but this returns a 2-4 digit number and is not recommended to be used; depreciated.

Setting the year,

document.write(d.setFullYear(1992));
// sets the year to 1992

// also can be used like, 
d.setFullYear(yyyy, mm, dd);

Time

To return the Time value of a Date object do,

d.getTime();
// returns the number of seconds from midnight

Adding seconds to a day, e.g. advance 1 day would be...

d.setTime(86400);
// adds 86400 seconds to the current date value
// 86400 seconds = 1 day

Hours, Minutes, Seconds,

This can be done like,

document.write(d.getHours());
// (0..23), returns the hour of the day, 11 = 11 O'clock

document.write(d.getMinutes());
// (0..59), returns the minutes, 23 = 23 minutes past

document.write(d.getSeconds());
// (0..59), returns the seconds, 12 = 12 seconds past

document.write(d.getMilliseconds());
// (0..999), returns the milliseconds past
// 1000 milliseconds in a second

Setting the values,

d.setHours(hour,min,sec,milli);

// so..
document.write(d.setHours(12));
// set to 12 noon

d.setMinutes(min,sec,milli);
document.write(d.setMinutes(2));

d.setSeconds(sec,milli);

d.setMilliseconds(milli);

To String

To return a Date object as a String value,

document.write(d.toString());
// returns Tue Dec 25 2007 12:44:05 GMT+0000 (GMT)

Calculations

Days in Month

This function returns the max days in the chosen month, so 2, 2008 returns => 29.

function daysInMonth(iMonth, iYear)
{
return 32 - new Date(iYear, iMonth, 32).getDate();
}

Thanks goes to Charlie for that...

Comparing Dates

if (Date.parse("11/11/2007") < Date.parse("11/11/2008")) {
document.write("wooah!");
}

NOTE: remember to use a lowercase if* rather than *If otherwise it'll throw up a missing ; error.