Provide a "clickable" field in the email that contains the current formatted
date / time. Reuse the existing date variables Y,y,m,n,S,T etc.

%dateformat(_formatString_)%

Format string is a placeholder for date, time and any special characters
(except for parentheses or percent signs)

The format variables are taken from the regular formats such as %Y% for 4-digit
Years, with the % symbols stripped

Supported Formats:
Y, y, n, m, e, d, k, H, l, I, M, S, tz_name, B, b, A, a, p1, p2, p

Examples:
%dateformat(A, e/n/Y, H:M)%
==>
Wednesday, 23/02/2018, 14:23

Created an attachment (id=8533) [details]
1.6 prerelease 146

Test version. This includes the new behavior from [Bug 24993] which supports
clicking the field to update the time. Note that the "Clean up" button
(customize the composer toolbar to get it) should be clicked before sending so
that the smartTemplate fields are removed / replaced with pure text.

Created an attachment (id=8535) [details]
1.6 prerelease 168

Latest version - the variable tab on ST4 prefs supports copying over the
%dateformat()% variable now.

Resolved Fixed: Version 2.0 - 23/12/2018