With the verb "to come" the past participle does not change and remains "come". The simple past tense (preterite) of this verb is "came". "Has came" is not a grammatically correct option here. Now the difference between "has come" and "came" is the function of these two tenses. In general, the perfect tense refers to something that has happened (or began) in the past and is relevant to the present. The camel *has come* under the hill (and is still there). The camel *came* under the hill (last night, for example, an action that occurred at a certain time in the past). The time *has come* (to do something in the present). The time *came* but we missed the opportunity (to do something at that time in the past). I hope this helps clear the differences up for you. If you're looking for a clearer explanation or want some practice exercises then I would recommend that you search for "present perfect or simple past tense" online, or message me if there's anything else you would like to clarify.

"Has came" is a grammatical mistake,it is always " has come".

That verb is in present perfect.It indicates an action that occurred in the past ,but it is still happening right now.It expresses a sequence of actions.

As far as speaking English in dialogues, the time has come or the time has came are both used but is more professional (formal). Typically I see these phrases used in speeches. Informally in America we usually say "I got to go," or any other farewell phrase you choose to use.