ACF Update Field into nested repeater field - php

Question

I'm trying to let users post from the front end into a nested ACF repeater field.
I've got the sub fields in the first repeater posting fine. But, I can't quite figure out how to get the nested repeater working properly.
Here's the code I have so far:
$event_field_key = 'field_535e6b9ffe3da';
$events[] = array(
'start-date' => $startDate,
'end-date' => $endDate,
'notes' => $_POST['p'.$p.'-notes'],
'start-end-times' => array(
'start-time' => '09:00', // would be dynamic
'end-time' => '17:00' // would be dynamic
)
);
update_field($event_field_key, $events, $post_id);
I'm not sure if I can just nest another array in there, or if I need to do something else.
[UPDATE]
I've just done this and it does input into the first row:
$event_field_key = 'field_535e6b9ffe3da';
$events[] = array(
'start-date' => $startDate,
'end-date' => $endDate,
'notes' => $_POST['p'.$p.'-notes'],
'start-end-times' => array(
'start-time' => '9:00',
'end-time' => ' 17:00'
)
);
update_field($event_field_key, $events, $post_id);
However, this code puts row 1 values both as 9 and row 2 values as 1.
So it looks like:
Row 1: start time: 9, end time: 9
Row 2: start time: 1, end time: 1
I can't seem to find any documentation on this, but it looks like it's possible, just a case of figuring out the syntax.

Answer 1

The fix was an array of arrays:
$event_field_key = 'field_535e6b9ffe3da';
$events[] = array(
'start-date' => $startDate,
'end-date' => $endDate,
'notes' => $_POST['p'.$p.'-notes'],
'start-end-times' => array(
array(
'start-time' => '09:00',
'end-time' => '17:00'
),
array(
'start-time' => '10:00',
'end-time' => '16:00'
)
)
);
update_field($event_field_key, $events, $post_id);