When God commissioned His people in the Old Testament to advance His rule over the land He commanded them to be holy.
"You shall be holy, for I the Lord your God am holy" (Lev.19:2).
In large part this meant they were to keep themselves from adopting the pagan practices that surrounded them.
As God commissions us today, this command continues to apply, and it involves a refusal to adopt the corrupt practices our culture seeks to make popular.
In this respect, holiness is never out of style for God's people... and the greatest effect of our lives often comes by simply being separate and distinct for Him.
"You are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light" (1 Pet.2:9).