Corrected entry: The episode is set in 2049. The lead astronaut mentions that her grandmother used to use the social media and blogging site Tumblr, in a fashion suggesting that the site is by this time a thing of the past, much like slide rules now. However, she is played by an actress who is at least in her late forties, meaning that if you do the math, her character would be more than old enough to have used Tumblr herself.
Correction: In addition to the implication, you're also assuming Lundvick is as old as the actor playing her. She could in fact be in her mid-30's (or younger). Plus, this episode aired in 2014, and while we know Tumblr continued to be widely used afterwards, it could have no longer been popular by the time Lundvick was old enough to use it in 2015 (perhaps her parents didn't want her using it until she was a teenager, if she is in fact 47 in 2049).
Mummy on the Orient Express - S8-E8
Corrected entry: When Clara is making her speech about how she has chosen not to leave The Doctor and that Danny is fine with it, watch her hair clip. It switches from the left side of her hair to the right side.
Correction: The clip stays on the left side of her hair the entire time.
Correction: The implication may be that much like Facebook now, it's something the older generation uses whereas the younger ones have already ditched it in favour of something else.