Let's see how to change time zone in Exchange Server. Let's say a previous Administrator built the server with the wrong time zone and now, after some years, people found that meetings received showing in a different Time zone. How to change it?

Go to your System Clock and change it

The first thing to check is if the System Clock of the user's computer is set with the proper Timezone setting.

View Time Zone settings for a specified user (Powershell)

For example:

Get-MailboxRegionalConfiguration "Adam_Bokiniec"

Resetting Time Zone settings for a specific user, this will let the user to choose his own Time Zone settings with next Outlook Web App (OWA) login:

Set-Mailbox -Identity "Adam_Bokiniec" -Languages $null

Reset Time Zone settings for all users

Get-Mailbox | Set-Mailbox -Languages $null

Set the Time Zone setting for a specified user

Set the Time Zone setting for a specified user, to identify the correct syntax for “TimeZone” parameter set the Time Zone” for a user in the OWA and use “Get-MailboxRegionalConfiguration”.

Set-MailboxRegionalConfiguration -Identity "Adam_Bokiniec" -Language en-GB -DateFormat "dd/MM/yyyy" -TimeFormat "HH:mm" -TimeZone "W. Europe Standard Time"

Set the Time Zone settings for all users

Get-Mailbox | Set-MailboxRegionalConfiguration -Language en-GB -DateFormat "dd/MM/yyyy" -TimeFormat "HH:mm" -TimeZone "W. Europe Standard Time"

Set the Time Zone settings for specified OU

Get-Mailbox -OrganizationalUnit "careexchange.in/Users” | Set-MailboxRegionalConfiguration -Language en-GB -DateFormat "dd/MM/yyyy" -TimeFormat "HH:mm" -TimeZone "W. Europe Standard Time"

Set default client language for Outlook Web App (OWA) for all users, here you need to use Language Codes witch can be found here: http://technet.microsoft.com/en-us/library/aa997435.aspx.

Once the default client language is specified when the users try to login for the first time in OWA, they are not prompted to choose a language and OWA Time Zone is picked up from the time zone of Client Access Server:

Set-OWAVirtualDirectory “OWA (Default Web Site)” -DefaultClientLanguage 2057

Changing the time zone setting in Microsoft Office 365

Log into your Office 365 account and locate and click the Settings (the gear) icon in the upper right corner of the page.

From the drop down, select Options :

Click again on Settings, on the left menu:

Now click on the tab Regional:

Select the correct time zone for your area and click Save:

Change Timezone and Language for all Users using Powershell (Office 365)

Finally, we will see how to change both Timezone and Language settings, for all Office 365 users, using Powershell for Azure.

For this we need to use the Set-MailboxRegionalConfiguration cmdlet in PowerShell (Azure - Office 365). Once we’ve connected to Office 365 using Powershell, we only need to run one cmdlet.

get-mailbox | Set-MailboxRegionalConfiguration -Language {language_ID} -TimeZone {name_of_the_TimeZone}

The Language ID is a number that corresponds to the correct language type. The following table shows you which number corresponds to which language.

The TimeZone consists of a String representing the time zone. Use the value from the middle column of the table below:

In the example below we will set all mailboxes in our Office 365 Tenant to the Language English (UK) and the GMT Standard Time zone.

get-mailbox | Set-MailboxRegionalConfiguration -Language 2057 -TimeZone "GMT Standard Time"