From here: executeScript, execute script, Arrays - Selenium IDE Commands Tutorial
var d= new Date(new Date().getTime() + 24 * 60 * 60 * 1000 * 5); var m=((d.getMonth()+1) < 10)?'0'+(d.getMonth()+1):(d.getMonth()+1); m=d.getFullYear()+"-"+m+"-"+d.getDate(); return m
(Change the 24 * 60 * 60 * 1000 * 5
to 24 * 60 * 60 * 1000 * 1
for tomorrows date)
Macro:
{
"Name": "date1",
"CreationDate": "2019-6-17",
"Commands": [
{
"Command": "open",
"Target": "https://ui.vision/demo/executescript",
"Value": ""
},
{
"Command": "executeScript_Sandbox",
"Target": "var d= new Date(new Date().getTime() + 24 * 60 * 60 * 1000 * 5); var m=((d.getMonth()+1) <10)?'0'+(d.getMonth()+1):(d.getMonth()+1); m=d.getFullYear()+\"-\"+m+\"-\"+d.getDate(); return m",
"Value": "var1"
},
{
"Command": "type",
"Target": "id=sometext",
"Value": "In five days is ${var1}"
}
]
}