Is there a unified platform that lists conference/journal deadlines?

WikiCFP offers this. To use this feature, you are required to register and sign in to your account.

Once you are logged in, find the Calls for Papers (CFPs) you are interested in and choose "Add to my list". (You can add multiple CFPs at a time if they appear in the same search results or "recent CFPs" list).

Then, from the sidebar, choose "My list" or "Timeline" to see all the deadlines for the conferences you have selected in your preferred format. Timeline view is pretty nice; it shows you the registration, submission, notification, and camera-ready deadlines, as well as the dates of the actual conference. Here is a screenshot:

However, WifiCFP relies on user-submitted content (for both original CFP submissions, and updates e.g., for deadline extensions). So the usefulness of this for you will depend on how active people in your field are on WikiCFP.

http://allconferencecfpalerts.com/ is a unified platform that lists conference / journal deadlines.

It also provides Open Access Research Sharing System - Share URL

Share-url link in the allconferencecfpalerts.com site is mainly built for researchers to share their academic information category wise. It is an open access platform to help researchers get more visibility and citations. This page is user-friendly so that authors can share information easily.

Authors who wish to post their Research information should register by creating Login id password. Login or registration is not required to view, search and download articles from the portal. All Share URL posts are categorized based on research area. User can search by title of the paper or author's name.