`first_published_at` not working properly in Wagtail - wagtail

Question

I have below PageDetail model defined:
class PostDetail(Page):
template = "Post_Detail.html"
body = RichTextField(blank=True)
search_fields = Page.search_fields + [
index.SearchField("body"),
]
content_panels = Page.content_panels + [
FieldPanel("body"),
]
but when I added 2 PageDetail pages (with 15 mins time interval), I found first_published_at was not working properly.
Q1: first_published_at of above 2 newly-added pages are the same Date and Time instead of 15 mins difference.
Q2: Even though I have WAGTAIL_USER_TIME_ZONES = ['Asia/Singapore'] in settings.py of Django Project and restarted the Django server, the first_published_at is still not in correct timezone.
Problem Solved
It turned out to be my silly mistake. In the template file (see below) of Post Index page, problem was fixed after I changed page.first_published_at to post.first_published_at.
{% for post in page.get_children %}
<h2>{{ post.title }}</h2>
<p>{{ post.first_published_at }}</p>
<!-- {{ post.specific.body|richtext }} -->
{% endfor %}

Answer 1

What are your Django settings for timezones? Do you have:
TIME_ZONE = ['Asia/Singapore']
USE_TZ = True
From the docs it looks to me like WAGTAIL_USER_TIME_ZONES is about the admin display parameter rather than what timezone the server is using.
Logged-in users can choose their current time zone for the admin interface in the account settings.