Unable to update my system using the obvious commands

entered sudo pacman -Syyu and pamac update but getting the same error

:: Synchronizing package databases...
 core.db failed to download
error: failed retrieving file 'core.db' from mirrors.piconets.webwerks.in : SSL certificate problem: certificate has expired
error: failed to synchronize all databases (download library error)
    ~  

pamac update                                                                                                            1 ✘ 
Synchronizing package databases...
https://mirrors.piconets.webwerks.in/manjaro-mirror/stable/core/x86_64/core.db: Unacceptable TLS certificate
Failed to synchronize databases
Refreshing AUR...                                                                                                                        
Nothing to do.                                                                                                                           
Transaction successfully finished.

The mirror you are pointing must renew their certificates. You can either wait they do so, or change mirror:

sudo pacman-mirrors -f 5