automatic playing of bag files

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hello everyone
my question is simple: I have two bag files to be played in sequence. Is there a way (for example, a launch file) to make this sequential execution automatic without need to perform it manually from the shell? I want, in particular, first bag to be played. After end of playing, second bag must be executed. I can't use something like

rosbag play bag1.bag bag2.bag

since first bag has a timestamp whose year is 1970, so second bag cannot be played before 40 years are past...

thanks for support