Communicate times you need to sleep
Some people in your life may not be familiar with the unique challenges connected with shift work and needing to sleep at unusual times. During the daytime when you need to sleep, some may think you are available for other activities.
To help people understand, you could tell them that during these "upside-down days" the only time you have available to sleep is during the day and you need to devote that time to sleep and nothing else. Another point that might help them understand is that workers who work during the day are not available during the night, when they need to sleep, and similarly, night workers are not available during their daytime sleep period.
Also, you can explain that daytime sleep is part of your obligation to your employer and yourself to maintain health. It may be helpful to mention that people with day jobs also have difficulties attending certain events during the daytime.