Which app has this notification icons?

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Well that G matches the logo of The Guardian (UK newspaper).

For the stylised t with a clock I suggest you ask him/her - there are an awful lot of apps out there, so it's rare that we can identify them all.

 

Try looking through the Settings >> Apps menu of your phone. Your Apps menu will reflect what apps are actually installed on it, and most Notification icons are going to be similar or at least closely resembling their respective App icons in some way. That's basically the purpose of an icon, to be a graphical identifier of a particular app or process, and to differentiate it from other apps/processes.