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How to update Gmail disaplayed timezone with ics attachment

I created an application to manage appointments in Lithuania. I managed to attach .ics file to an email where clients could see their upcomming appointments. I noticed that some non-it or just temporarily visiting the country users have other timezones set on their devices which most of the times confuses them. Is it possible to make the displayed timezone fixed to Europe/Vilnius?

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Here's the .ics attachment from the same email:

BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:grozissaviems
X-WR-TIMEZONE:Europe/Vilnius
METHOD:PUBLISH
BEGIN:VTIMEZONE
TZID:Europe/Vilnius
X-LIC-LOCATION:Europe/Vilnius
END:VTIMEZONE
BEGIN:VEVENT
UID:5411@grozissaviems.lt
SEQUENCE:0
SUMMARY:Testavimo paslauga
DTSTAMP:20240514T124512Z
DTSTART:20240515T130000Z
DTEND:20240515T140000Z
DESCRIPTION:Daugiau informacijos http://local.grozissaviems.lt/premium/vizitai
LOCATION:Vilniaus g. 38\, Telšiai\, Telšių rajono savivaldybė\, Lietuva
STATUS:CONFIRMED
BEGIN:VALARM
TRIGGER:-PT30M
ACTION:DISPLAY
END:VALARM
END:VEVENT
END:VCALENDAR

The DTSTART and DTEND are UTC dates in Ymd\THis\Z format.

I also tried the below and it doesn't work:

DTSTART;TZID=Europe/Vilnius:20240515T130000
Solution 
  • BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:grozissaviems
X-WR-TIMEZONE:Europe/Vilnius
METHOD:PUBLISH

BEGIN:VTIMEZONE
TZID:Europe/Vilnius
X-LIC-LOCATION:Europe/Vilnius

# Added standard time definition to clarify the timezone details. 

BEGIN:STANDARD
DTSTART:20240515T130000
TZOFFSETFROM:+0300
TZOFFSETTO:+0300
TZNAME:EET
END:STANDARD
END:VTIMEZONE

BEGIN:VEVENT
UID:5411@grozissaviems.lt
SEQUENCE:0
SUMMARY:Testavimo paslauga
DTSTAMP:20240514T124512Z

# Removed 'Z' suffix.
# 'Z' suffix indicates UTC time, which was causing confusion 
# as it didn't specify the Europe/Vilnius timezone.

DTSTART;TZID=Europe/Vilnius:20240515T130000
DTEND;TZID=Europe/Vilnius:20240515T140000
DESCRIPTION:Daugiau informacijos http://local.grozissaviems.lt/premium/vizitai
LOCATION:Vilniaus g. 38\, Telšiai\, Telšių rajono savivaldybė\, Lietuva
STATUS:CONFIRMED

BEGIN:VALARM
TRIGGER:-PT30M
ACTION:DISPLAY
END:VALARM
END:VEVENT
END:VCALENDAR