How do i get older twitter data?



Am i right in assuming the Twitter API is only for current twitter feeds and if you want anything from over 2 months ago you cannot do so via the API? Does anyone know how you can get a dataset for further analysis from twitter, i need about 6 weeks worth of data based on some keywords from november last year. I have found a site whom visually show the data but no idea how i can do this myself. Any help would be really appreciated as it is for my masters dissertation and i’m running out of time.