AWS Lambda: Accuracy of system clock
AWS Lambda clocks are synchronized using NTP, so the accuracy is as good as what NTP can provide
Quoting from what I found in the Lambda documentation here
TZ – The environment's time zone (UTC). The execution environment uses NTP to synchronize the system clock
- https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html
- https://docs.aws.amazon.com/lambda/latest/dg/lambda-dg.pdf