UX Improvements

[jstet]

• [x] Write somewhere that if e.g. the day of a date is unclear that ppl should select the undefined option
• [x] Do we need a dropdown for years that start with 1800? should we limit that to maybe starting from 1900 or smth to make selecting the year easier?

[jstet]

Start year depends on question, e.g. 1930 for stations