Timetable app for myself
I would change your setup code to take a list of lists, where the inner lists are lists of subjects on that day and the outer list collects all these lists:

schedule = [['Spanish', 'Spanish', 'Music', 'Music', 'English Literature', 'English Literature', 'History', 'History'],
            ...]

def format_day(day_schedule):
    return "\n" + "\n".join("{}       {}".format(i, subject)
                            for i, subject in enumerate(day_schedule, 1))

today = date.datetime.today().weekday()

try:
    the_day = format_day(schedule[today])
except IndexError:
    the_day = ''
try:
    tomorrow = format_day(schedule[today + 1])
except IndexError:
    tomorrow = format_day(schedule[0])


This could actually be moved into the class, which could just take the schedule and day as parameters (which would make it a lot easier to run this, e.g for two different schedules):

import datetime
import sys
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import (QHBoxLayout, QApplication, QWidget, QLabel)
from PyQt5.QtGui import (QIcon, QPixmap)


def format_day(day_schedule):
    return "\n" + "\n".join("{}       {}".format(i, subject)
                            for i, subject in enumerate(day_schedule, 1))


class Timetable(QWidget):               

    def __init__(self, schedule, day):
        super().__init__()
        self.schedule = schedule
        self.day = day
        self.init_UI()


    def init_UI(self):
        try:
            today = format_day(self.schedule[self.day])
        except IndexError:
            today = ''
        try:
            tomorrow = format_day(self.schedule[self.day + 1])
        except IndexError:
            tomorrow = format_day(self.schedule[0])

        if self.day &lt;= 5:
            today_header = '&lt;b&gt;Today\'s Timetable:&lt;\b&gt;'
            tomorrow_header = '&lt;b&gt;Tomorrow\'s Timetable:&lt;\b&gt;'
        else:
            today_header = ''
            tomorrow_header = '&lt;b&gt;Monday\'s Timetable:&lt;\b&gt;'

        if self.day in (4, 5, 6):
            lbl = QLabel(self)
            pixmap = QPixmap('weekend.jpg')
            smaller_pixmap = pixmap.scaled(160, 300, Qt.KeepAspectRatio, Qt.FastTransformation)
            lbl.setPixmap(smaller_pixmap)
            if self.day == 4:
                lbl.move(-3, 162)
            else:
                lbl.move(-3, 0)
            lbl.show()      

        title0 = QLabel(today_header, self)
        title0.move(5, 5)
        schedule0 = QLabel(today, self)
        schedule0.move(5, 16)

        title1 = QLabel(tomorrow_header, self)
        title1.move(5, 150)
        schedule1 = QLabel(tomorrow, self)
        schedule1.move(5, 160)

        self.setGeometry(7, 30, 150, 287)
        self.setFixedSize(self.size())
        self.setWindowTitle('Timetable')
        self.setWindowIcon(QIcon('icon.png'))      
        self.show()


if __name__ == '__main__':
    app = QApplication(sys.argv)

    schedule = [['Spanish', 'Spanish', 'Music', 'Music', 'English Literature', 'English Literature', 'History', 'History'],
                ...]
    today = date.datetime.today().weekday()
    ex = Timetable(schedule, today)
    ex.show()
    sys.exit(app.exec_())
    #created with PyQt5 using Python 3.5


Note that I also renamed some of your variables (there is now a today and a today_header and a tomorrow and tomorrow_header.