Jacobs always drew his stories as being contemporary and based on real environments, so the first few titles have a 1950s look and feel while the last installments are decidedly 1970s. One exception to this rule is, again, "Time Trap", which starts in the present (i.e. early 1960s) but whose action, due to a sabotaged malfunctioning time machine, largely takes place in the 51st century, and includes a short ventures in medieval times and a stopover in the Jurassic period. Post-Jacobs stories are so far integrated in the chronology of the first ones or precede it, therefore taking place in the 1940s, 1950s and 1960s.