For Newer version of Edwiser RemUI theme (It will work for version Edwiser RemUI 3.7.5 and above)

Add this CSS in Edwiser RemUI general settings >> Custom CSS section

#nav-drawer-container a[data-key="calendar"] {
display: none;
}


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For Older version of Edwiser RemUI theme (It will work for versions till Edwiser RemUI 3.5.11, Edwiser RemUI 3.6.7 and Edwiser RemUI 3.7.4)

Add this CSS in Edwiser RemUI general settings >> Custom CSS section

li.site-menu-item a[data-key="calendar"]{
display: none;
}