Date parsing, does not take slovene locale

[Mojster]

Log entry:
SEARCH#Android#SLO#sikmb#BIB#sikmb#02-okt-2017 07:04:00.721#ADV##0#0#0#2#8#((šola AND luči)) NOT (DT=D) NOT RS=D and (DP=08 OR DP=XX) NOT NH=1

filter part from pipeline:

grok {
			match => {"message" => "%{DATA:act}\#%{DATA:interface}\#%{DATA:country}\#%{DATA:acronym}\#%{DATA:typeDB}\#%{GREEDYDATA:leftovers}"}
		}
		if [act] == "CONN" {
			drop { }
		}
		ruby {
			code => "event.set('acronym', event.get('acronym').upcase)"
		}
		
		mutate{
			split => {"leftovers" => "#"}
		}
		
		if [act] == "AUTH" {
			mutate{
				add_field => {
					"date" => "%{leftovers[1]}"
					"userID" => "%{leftovers[2]}"
				}
				remove_field => [leftovers]
			}
		} else if [act] == "DISP" {
			mutate{
				add_field => {
					"date" => "%{leftovers[0]}"
					"outputType" => "%{leftovers[1]}"
					"userID" => "%{leftovers[2]}"
				}
				remove_field => [leftovers]
			}
		} else if [act] == "SEARCH" {
			mutate{
#				WORKAROUND ŠUMNIKI
				add_field => {
					"url" => ""
					"date" => "%{leftovers[1]}"
					"mode" => "%{leftovers[2]}"
					"stZadetkov" => "%{leftovers[7]}"
				}
				merge => {"url" => "leftovers[9]"}
				remove_field => [leftovers]
			}
		} else if [act] == "RESR" or [act] == "PROL" or [act] == "CRES" {
			mutate{
				add_field => {
					"date" => "%{leftovers[1]}"
					"userID" => "%{leftovers[2]}"
					"serialNum" => "%{leftovers[3]}"
				}
				remove_field => [leftovers]
			}
		}
		
		date {
			locale => "sl-SI"
			match => ["date", "dd-MMM-YYYY HH:mm:ss.SSS"]
			timezone => "Europe/Ljubljana"
			target => "date"
		}
		
		mutate{
			join => {"url" => ""}
			add_field => {"inputType" => "MCOBISS"}
		}

My problem is, that my date 02-okt-2017 07:04:00.721 is written with using Slovenian locale
http://www.localeplanet.com/java/sl-SI/index.html

I've tried in the locale setting both option sl and sl_SI.
I'm using the latest LS 5.6.3.
I've posted this on ES discus, but because of the weekend ahead, I've decided to duplicate the post here.

Is there any option to process this or should I just do a gsub and just replace them?

[Mojster]

Found a fix.

Date plugin does not suport Slovenian locale (sl, sl_SI, sl-SI) but a I found out with testing, it does support, Serbian (sr_Latn_RS) and the 3char months are identical.