Today I tried to upload my certificate to AWS IAM.

Command line:

C:\SSL>aws iam upload-server-certificate 
--server-certificate-name wildcard_domain_net 
--certificate-body file://public.crt 
--private-key file://private.key

And I got this error:

A client error (SignatureDoesNotMatch) occurred when calling the UploadServerCertificate operation: 
Signature expired: 20160512T092519Z is now earlier than 2016 0512T092623Z (20160512T094123Z - 15 min.)

This means my local time is not correct, and this happened to me because my PC has been recently disconnected from our domain so it was still configured to get NTP data from the domain server.

To quickly fix this just run cmd.exe as Administrator and execute:

C:\Windows\system32>w32tm /config /manualpeerlist:pool.ntp.org,0x8 /syncfromflags:MANUAL

Followed by:

C:\Windows\system32>w32tm /config /update