Elapsed Time is very difficult for elementary and middle school aged templates.
They have difficulty keeping track of the hours and minutes as they transition forward and backward to compute elapsed time - either starting with a time and moving forward for some finite time period OR vice versa, given an ending time and moving backward to compute an unknown starting point.
These FREE paper ruler templates (ON 11 x 17 inch PAPER) make it easy for kiddos to understand the time calculations in a linear fashion - visible medium. A teacher or school can purchase much more expensive plastic ones, but these are templates are FREE and the student can write on them. Additionally, the teacher can Xerox copy - print out 7 sheets of 11 x 17 paper, cut along the dotted line, and have 28 student ruler aids to provide students a visual of 12 hours in a day - PM. And, this resource is FREE, unlike a plastic, commercial ruler.
Start with time only in the AM - Ante Meridiem or PM - Post Meridiem. Until students are adept at one 12 hour period WITHOUT going over lunch (12 PM), it is not recommended to ask elapsed time problems from AM to PM or vice versa. It confuses them to no end.
Also, so many students do not know there are 24 hours in a day - the time it takes the earth to rotate ONE time on its axis. Each time zone is 15 degrees - 24 in all in the world (5 Time Zones in the United States - Eastern, Central, Mountain, Pacific, Alaska). So, 15 degrees multiplied by 24 is 360 degrees. The total amount of measure in a circle or sphere like the Earth. I am a firm believer that students should know this type of information...at least 24 hours in a day...why 24?...24 time zones in the world...5 time zones in the United States...and name them...and they are all 1 hour apart. My unsolicited thoughts.
Good luck with your students!