It was never shown, it happened between the events of the 1996 movie and the 2005 reboot.
The 50th anniversairy special will go into more detail about it.
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There is no episode with the eighth Doctor regenerating, he was only in the 1996 movie, and when the show returned in 2005 it was with the ninth Doctor.
If you think about it, there have been a lot of Doctor Who episodes in which the daleks seem to be wiped out, but are shown in other episodes as not having been destroyed. Therefore enough Daleks must have survived. Also, in the Doctor Who version of the 22nd Century, after the Dalek wars between the daleks and earth, all the Daleks suddenly dissapeared. They in truth had gone to fight the time war against the Time Lords. They were then almost all destroyed. The reason there are no episodes of Doctor Who set in the time war is that when the show returned Russell T. davies wanted to picture the Doctor as the last survivor of his race, and to keep the events of the Time War a mystery, and give little hints to some of the things hat happened in the Time War.
The Time War.
Doctor Who - 1963 The Escape 1-7 is rated/received certificates of: Australia:PG Australia:G (video rating) UK:12 (DVD rating) UK:U (video rating)
if by 'Janie' you mean 'Jamie', then both he and Zoe were sent to their respective times and had their memories wiped during the last episode of 'The War Games.'