Remember only bits and pieces. There is a lift and a key to it. Instead of pressing the floor number, a year is pressed and the lift will travel to that period (example - 1936). There is a girl who got this key from an old man. She travels to different time periods. She finds another girl in some old fashioned house, befriends her and she is brought to the new world with her. The old time girl is stunned by seeing the huge buildings and traffic. Guess it was a movie. Not sure if it was a series!
You're describing the 1999 film; "Time at the Top".
14-year old Susan Shawson travels back in time in her building's elevator. As altered by a retired physicist living in her building, it transports her from Philadelphia of 1998 back to the same place in 1881. There she meets Victoria Walker, a girl her own age in need of assistance with her own family problems. Gradually discovering the power of her time machine, Susan, Victoria, and her young brother Robert travel back and forth in time and succeed in changing both the past and the future.
One of the key features of the film is a time-travelling elevator. The scene of Victoria being surprised by traffic is at 1:08:00