Following are a number of back-translations as well as a sample translation for translators of Zephaniah 1:15:

• Kupsabiny: “On that day God will show his anger. Great (is) the suffering and pain on that day. The land will be ruined and destroyed. Darkness will come to overshadow the land/world because dark clouds will cover (it).” (Source: Kupsabiny Back Translation)
• Newari: “That day will be a day of angry,
  a day of distress and anguish,
  a day of trouble and destroyed
  a day of darkness and not happiness,
  a day of clouds and very blackness,” (Source: Newari Back Translation)
• Burmese (translation by A. Judson): “That day is a day of anger,
  a day of suffering affliction and distress,
  a day of wiping out and destruction,
  a day of concealed light and darkness,
  a day of cloud cover and overspreading thick darkness,” (Source: John Hans de Jong in The Bible Translator 2017, p. 64ff. )
• Hiligaynon: “That is the day that God will-show his anger. That day of difficulty, pain/anguish, destruction, and defeat. That day (is) dark and has-dark-rain-clouds,” (Source: Hiligaynon Back Translation)