Single Export:
New-MailboxExportRequest –Mailbox company.holidays –FilePath \\SERVER01\PST\hol.pst -IncludeFolders “#Calendar#”
Single Import:
New-MailboxImportRequest –Mailbox foo.user –FilePath \\SERVER01\PST\hol.pst -IncludeFolders “#Calendar#”
Mass Import:
$users = Get-Mailbox -ResultSize Unlimited ForEach ($u in $users) { New-MailboxImportRequest –Mailbox $u –FilePath -IncludeFolders “#Calendar#” }
NOTES:
https://4sysops.com/archives/how-to-add-holidays-to-the-exchange-calendar-with-powershell/