docs(datepicker): correct typos (#10339)

Author: julianobrasil

src/lib/datepicker/datepicker.md

@@ -53,15 +53,16 @@ year containing the `startAt` date.
 
 #### Watching the views for changes on selected years and months
 
-When a year or a month is selected in `multi-year` and `year` views respecively, the `yearSelected`
+When a year or a month is selected in `multi-year` and `year` views respectively, the `yearSelected`
 and `monthSelected` outputs emit a normalized date representing the chosen year or month. By
-"normalized" we mean that the dates representing a year will have their month set to January and
+"normalized" we mean that the dates representing years will have their month set to January and
 their day set to the 1st. Dates representing months will have their day set to the 1st of the
 month. For example, if `<mat-datepicker>` is configured to work with javascript native Date
 objects, the `yearSelected` will emit `new Date(2017, 0, 1)` if the user selects 2017 in
-`multi-year` view. Similarly, `monthSelected` will emit `new Date(2017, 1, 0)` if the user
+`multi-year` view. Similarly, `monthSelected` will emit `new Date(2017, 1, 1)` if the user
 selects **February** in `year` view and the current date value of the connected `<input>` was
-something like `new Date(2017, MM, dd)` (the month and day are irrelevant in this case).
+set to something like `new Date(2017, MM, dd)` when the calendar was opened (the month and day are
+irrelevant in this case).
 
 Notice that the emitted value does not affect the current value in the connected `<input>`, which
 is only bound to the selection made in the `month` view. So if the end user closes the calendar