You know when someone says 'Don't go in there' or 'Whatever you do, don't touch'? There's something the Anderson children decide is worth the risk and, without really doing much, they find themselves back in the past!
An exciting and unlikely adventure awaits them in 1966, ends in panic, but they get back safely, only to realise they've left the dog behind, so they have to return to the '60s to search for him. Every time they subsequently try to get home, they end up in a different decade, witnessing a key or notable event in history. Initially, they go back further in time, but then realise how to alter the path they are taking, to finally get back to the present.
Remember, these are children of the 2000s, so losing your favourite trainers in the '40s isn't cool at all and not being able to use your mobile phone before the '80s is unfathomable!