A Scriptable widget that shows upcoming calendar events to mimic the built-in Calendar widget, with some modifications.

mz_calendar_widget.js

// Variables used by Scriptable.
// These must be at the very top of the file. Do not edit.
// icon-color: red; icon-glyph: calendar-alt;

// This widget was created by Max Zeryck @mzeryck

// Note: before using this script in a widget, change const TEST_MODE to true and run it in the Scriptable app.
// The app will prompt you to give calendar access, and then show a preview of the widget.
// Make sure to change it back to const TEST_MODE = false prior to adding it to a widget. Happy coding!

const IMAGE_SOURCE = "Unsplash"
const TERMS = "nature,water"

const FORCE_IMAGE_UPDATE = false
const TEST_MODE = false

// Store current datetime
const date = new Date()

// If we're running the script normally, go to the Calendar.
if (!config.runsInWidget && !TEST_MODE) {
  const appleDate = new Date('2001/01/01')
  const timestamp = (date.getTime() - appleDate.getTime()) / 1000
  const callback = new CallbackURL("calshow:"+timestamp)
  callback.open()
  Script.complete()
  
// Otherwise, create the widget.  
} else {

  let widget = new ListWidget()
  
  // Format the date info
  let df = new DateFormatter()
  df.dateFormat = "EEEE"
  let dayOfWeek = widget.addText(df.string(date).toUpperCase())
  let dateNumber = widget.addText(date.getDate().toString())
  dayOfWeek.font = Font.semiboldSystemFont(13)
  dateNumber.font = Font.lightSystemFont(34)
  
  // Find future events that aren't all day and aren't canceled
  const events = await CalendarEvent.today([])
  let futureEvents = []
  for (const event of events) {
      if (event.startDate.getTime() > date.getTime() && !event.isAllDay && !event.title.startsWith("Canceled:")) {
          futureEvents.push(event)  
      }
  }
  
  // If there is at least one future event today
  if (futureEvents.length != 0) {

    dayOfWeek.textColor = Color.red()
    widget.addSpacer()
    
    let titleOne = widget.addText(futureEvents[0].title) 
    titleOne.font = Font.mediumSystemFont(14)
    
    widget.addSpacer(7)
    
    let timeOne = widget.addText(formatTime(futureEvents[0].startDate))
    timeOne.font = Font.regularSystemFont(14)
    timeOne.textColor = Color.gray()
   
    // If we have multiple future events, show the following one
    if (futureEvents.length > 1) {
      
        // We only have room for single-line event names
        titleOne.lineLimit = 1
        
        widget.addSpacer(12)
        
        let titleTwo = widget.addText(futureEvents[1].title) 
        titleTwo.font = Font.mediumSystemFont(14)
        titleTwo.lineLimit = 1
        
        widget.addSpacer(7)
        
        let timeTwo = widget.addText(formatTime(futureEvents[1].startDate))
        timeTwo.font = Font.regularSystemFont(14)
        timeTwo.textColor = Color.gray()
    }
      
  // If there are no future events today
  } else {
      dayOfWeek.textColor = Color.white()
      dateNumber.textColor = Color.white()
      
      let files = FileManager.local()
      const path = files.joinPath(files.documentsDirectory(), "mz_calendar_widget.jpg")
      const modificationDate = files.modificationDate(path) 
      
      // Download image if it doesn't exist, wasn't created today, or update is forced
      if (!modificationDate || !sameDay(modificationDate,date) || FORCE_IMAGE_UPDATE) {
         try {
            let img = await provideImage(IMAGE_SOURCE,TERMS)
            files.writeImage(path,img)
            widget.backgroundImage = img
         } catch { 
            widget.backgroundImage = files.readImage(path)
         }
      } else {
         widget.backgroundImage = files.readImage(path)  
      }
      
      // Add overlay to image
      let gradient = new LinearGradient()
      gradient.colors = [new Color("#000000",0.5), new Color("#000000",0)]
      gradient.locations = [0, 0.5]
      widget.backgroundGradient = gradient

      widget.addSpacer()
  }
  
  // Finalize widget settings
  widget.setPadding(16,16,16,0)
  widget.spacing = -3
  
  Script.setWidget(widget)
  widget.presentSmall()
  Script.complete() 
}

// Helper function to interpret sources and terms
async function provideImage(source,terms) {
    
    if (source == "Bing") {
        const url = "http://www.bing.com/HPImageArchive.aspx?format=js&idx=0&n=1&mkt=en-US"
        const req = new Request(url)
        const json = await req.loadJSON()
        const imgURL = "http://bing.com" + json.images[0].url
        const img = await downloadImage(imgURL)
        const rect = new Rect(-78,0,356,200)
        return cropImage(img, rect)
        
    } else if (source == "Unsplash") {
        const img = await downloadImage("https://source.unsplash.com/featured/500x500/?"+terms)
        return img
    } 

}

// Helper function to download images
async function downloadImage(url) {
   const req = new Request(url)
   return await req.loadImage() 
}

// Crop an image into a rect
function cropImage(img,rect) {
   
    let draw = new DrawContext()
    draw.respectScreenScale = true
    
    draw.drawImageInRect(img,rect)  
    return draw.getImage()
}

// Formats the times under each event
function formatTime(date) {
    let df = new DateFormatter()
    df.useNoDateStyle()
    df.useShortTimeStyle()
    return df.string(date)
}

// Determines if two dates occur on the same day
function sameDay(d1, d2) {
  return d1.getFullYear() === d2.getFullYear() &&
    d1.getMonth() === d2.getMonth() &&
    d1.getDate() === d2.getDate()
}

Hi, how to show TODAY all day events?