As a fairly new teacher, I was struggling to come up with a way to efficiently track how many times a student was using the bathroom. The Bathroom log I was given had a place for them to put down their name, date and such. Students took forever to write their names and a lot of times they did not even write their name. I ended up creating this excel spreadsheet that has their name printed already and 3 available columns. The idea is that they get 3 passes for the month since there is only 3 columns. This prevents over-use of bathroom passes. You can also provide positive reinforcement by giving out 5 extra points to their grade for not taking the bathroom pass for the Marking Period. I have personally seen it work wonders in my classroom and hope it works for yours. Feel free to change the excel file to meet you individual needs.
Instead of having students put down the time that they came in, I thought it is more meaningful for them and for yourself to have your students calculate the number of minutes that they were late. I have my students calculate how many minutes they are late rather than putting in some time, which students could care less about and this process gives them more context. After enough practice with your classroom, students will surely be on track or at least be aware of the magnitude of their lateness.
Additional Thoughts
Instead of having students put down the time that they came in, I thought it is more meaningful for them and for yourself to have your students calculate the number of minutes that they were late. I have my students calculate how many minutes they are late rather than putting in some time, which students could care less about and this process gives them more context. After enough practice with your classroom, students will surely be on track or at least be aware of the magnitude of their lateness.