When you try to book, you have to have some dates to work with. The system then searches for flights and tells you the best price on each day. I just keep watching for a $5 flight with a date and time that suits me.
Today I managed to get flights to Chch and back, got all the names filled in, got the credit card details and just as it was about to give me my confimation receipt........... the site jammed! [

!]
I rang the credit card coy to see if I had been charged, not yet....... so waited until the rush was over and rang Jetstar, even though I had an email comfirming my reservation.... the whole page had no itinery and no value had been charged to my card..... they could do nothing. All the seats had been booked. Poobum, double poobum.
Chch and back for $28, $5 each way, per person and $2 fee per ticket. was worth following through.
Never mind, next time............. then Air NZ tossed their hat into the ring......... limited flights for $3 [:0]........ will have to watch them now as well.