How I can insert a date a Custom Field in the shortcode

For example something like this ?

[schedule from=”2018-08-10T15:00″ to=”[acf field=”fecha_cierre”]”] [acf field=”formulario”] [/schedule]

[acf field=”fecha_cierre”] it is a custom field make with ACF-Data Piker

What is the “T” on the date??

Gracias
Juan