These four events repeat every 'tropical' year (365 days, 5 hours, 49 minutes), so they become later by about six hours, or (if there has been an intervening leap day) earlier by about 18 hours, from one year to the next.
The three distinctive signs and symptoms of autism include problems with verbal and nonverbal communication, difficulties with social interaction, and repetitive behaviors or narrow, obsessive interests. There are three distinctive symptoms of autism.
Autism spectrum disorder. Autism spectrum disorder (ASD) is a developmental disorder. It often appears in the first 3 years of life. ASD affects the brain's ability to develop normal social and communication skills. The exact cause of ASD isn't known. It's likely a number of factors that lead to ASD.